Anatomical and physiological studies on the growth of the inner ear of the albino rat 1 (1923)

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Wada T. Anatomical and physiological studies on the growth of the inner ear of the albino rat. (1923) Memoirs of the Wistar Institute of Anatomy and Biology, No. 10, Philadelphia.

Rat Inner Ear (1923): I. Cochlea growth | II. Inception of hearing and cochlea growth | III. Growth of largest nerve cells in ganglion vestibulare | Final Summary | Literature Cited

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Anatomical and Physiological Studies on the Growth of the Inner Ear of the Albino Rat

I. On the Growth of the Cochlea

As noted above, I have selected from at least seven serially sectioned cochleas in each age group, four for this study, taking one section in good condition from each labyrinth. From these four sections the average values were taken for each age. Table 1 gives the data for the rats used here. As we see, sometimes two, sometimes three animals were used at each age to get the four best-prepared sections which corresponded. Determinations accordingly to sex and side, therefore, cannot be based on like numbers.

In the following text we shall often refer to the I, II, III and IV turns of the cochlea. This calls for a word of explanation. As the cochlea of the rat has nearly 2^ complete turns, four cochlear canals are usually obtained in the radial vertical sections, as prepared by me (fig. 3). Therefore, turn I does not mean the first complete turn, but about the middle part of the basal turn; turn II about the beginning of the middle turn; turn III about the middle part of the middle turn, and turn IV about the beginning of the apical turn of the cochlea. Usually the cochlea has been divided for description by the authors into the first, second, and third turns, or more definitely into the basal, middle, and apical turns. For the purpose of this study, however, it is desirable to adopt the divisions given above, because here measurements are largely employed, and there are some differences in size, volume, and arrangement of structures, even between the beginning and end of the same turn.

At all events, it is to be kept in mind that such divisions are arbitrary, as the changes in the elements take place in a graded manner.

A. On the growth of the radial distance between the two spiral ligaments

(fig. 3, 1-1, 2-2)

As we have usually four sections of the ductus cochlearis, therefore four spiral ligaments in one radial vertical section, there are two radial distances presented, the first, figure 3, 1-1, connecting the two basal sections of the ductus on opposite sides, and the second, figure 3, 2-2, connecting the two apical sections. These distances measure the radial breadth of the membranous cochlea and of the modiolus combined at these levels.

Online Editor - TABLE 1 (to be formatted)

TABLE 1 Data on the albino rats used for the study of the cochlea AGE BODY WEIGHT BOOT LENGTH BEX SIDE HEARING days grams mm. 1 5.3 48 d" R. L. 1 4.2 47 o" R. L. 3 8.8 60 a" R. 3 7.1 54 o" R. L. 3 8.2 56 9 R. 6 10.2 64 9 R. L. 6 11.0 62 tf R. L. 9 9.1 58 9 R. L. 9 9.8 57 tf R. L. =fc 12 13.0 70 a 1 L. + 12 11.9 68 9 R. L. + 12 14.8 72 d" L. + 15 13.0 74 0" R. + 15 13.5 75 9 R. + 15 13.0 74 9 R. L. + 20 30.0 96 cf R. L. + 20 28.0 94 c? R. L. + 25 38.4 107 9 R. L. + 25 34.2 101 9 R. L. + 50 60.0 128 9 R. L. + 50 57.5 121 9 R. L. + 100 145.6 176 a 1 L. + 100 102.5 154 9 R. + 100 100.5 152 9 R. L. + 150 153.5 184 9 R. + 150 188.9 191 d 1 R. L. + 150 198.8 192 <? R. + 250 133.5 178 9 R. L. + 263 140.3 171 9 R. L. + 365 205.4 202 0" L. + 365 170.4 182 9 R. L. + 368 179.0 196 9 R. + 546 282.1 222 <? R. L. + 546 227.1 204 rf R. L. +

In table 2 (chart 1) are entered the values for the radial distances found between the two spiral ligaments in fourteen age groups, from one to 546 days. As we see, the average value of the two distances grows rapidly from birth till six days of age. After that period the value increases gradually till twenty days, while after twenty days the increase is very slight indeed. The ratios between 1 and 12, 1 and 20, and 1 and 546 days show these relations.

Online Editor - TABLE 2 (to be formatted)

TABLE 2 Radial distance between the two spiral ligaments in radial-vertical section (chart 1, figure 3) AVERAGE DISTANCE BETWEEN TURNS IN M AGE TTTT'nWP I-II III-IV I-II plus III-IV days grams mean 1 5 1410 925 1168 3 8 1560 1025 1S93 6 11 1650 1175 1413 9 10 1635 1225 1430 12 13 1640 1233 1437 15 13 1655 1235 1445 20 29 1645 1250 1448 25 36 1620 1250 1435 50 59 1615 1253 1434 100 112 1663 1270 1467 150 183 1618 1290 1454 257 137 1655 1275 1465 366 181 1635 1285 1460 546 255 1680 1265 1473 Ratios 1 12 days 1 1.2 1 20 " 1.2 1 546 " 1.3

In table 3 are given the average ratios between two radial distances between I-II and III-IV at four ages. Here we can also see a rapid increase in the ratio from one to eight days of age, while afterwards the ratios rise very gradually. The data in table 2 show that at nine days the mean diameter of the bony cochlea as thus measured is approximately 97 per cent of the value at maturity. The cochlea thus attains nearly its full size at an early age. Chart 1 illustrates this point.

Online Editor - TABLE 3 (to be formatted)
TABLE 3 Condensed Ratios of distances between the two spiral ligaments along 1-1 (turns I-II) and along 2-2 (turns III-IV), figure 3 AGE BODY WEIGHT Ratios between the two distances turns I-II and III-IV days grams 1 5 . 1:0.66 8 11 0.72 18 21 0.75 213 138 0.77

Chart 1 The radial distance between the spiral ligaments, turns I-II and III-IV, table 2, figure 3 (/-/) and (-).

Radial distance at turns I-II.

Radial distance at turns III-IV.

Average radial distance for the two foregoing measurements.

All the charts are plotted on age.

The scale for age changes at 50 days. From to 50 days one interval is equal to five days. From 50 days on, one interval is equal to twenty-five days.

Unless otherwise stated, the measurements recorded in these charts have been made on radial-vertical sections.

B. On the growth of the tympanic wall of the ductus cochlearis

Figures 4 to 12 show the appearance in outline at birth, at three six, nine (not hearing), nine (hearing), twelve, twenty one hundred, and 546 days, respectively. These figures have been drawn from the best corresponding sections at the beginning of the middle turn of the cochlea, figure 3, turn n, which I have selected as the type, as did Retzius.

The fact, demonstrated by many authors, Bottcher ('69), Retzius ('84), and others, that development progresses from the basal to the apical turn is confirmed in the albino rat.

In the albino rat the development of the cochlea, and especially of the ductus cochlearis, is somewhat retarded as compared with man, and the papilla with its elements developed in a great measure during the first ten days after birth.

As we see in figure 4, the ductus cochlearis in the new-born rat is very immature. It is remarkable that the space which lies in adult rats axialward of the papilla spiralis between the membrana tectoria and the limbus spiralis-sulcus spiralis internus (fig. 10) is not yet to be seen. Instead of the space, there is the socalled greater epithelial ridge (der grosse Epithelwulst of Bottcher) figure 4, G. consisting of pseudostratified epithelial cells. These long and narrow cells lie pressed very closely together with their large oval nuclei at various heights. The surface of the prominence sinks slightly in its center, and at the outer end of the prominence more rapidly, where it passes over into the socalled lesser epithelial ridge fig. 4, L. (der kleine Epithelwulst) at an obtuse angle.

The latter is, of course, a relatively small prominence, making up the greater part of the papilla spiralis. The pillar cells of Corti lie with their upper ends at the most inner part of the surface of the lesser ridge just in the angle with the greater ridge. They form two entirely separate rows of cells, the inner and the outer, but so close together that we cannot detect any space between them. Only the protoplasm of the inner pillar cell is more transparent above the nucleus, and on the inward side there is a thin rod passing from the upper end to the lower part near the base. This transparent area is not the locus of the future tunnel of Corti, but marks the protoplasmic change into the pillar, as the transparent substance condenses into the rod. We can see this change beginning in the basal turn before it appears in the apical turn of the cochlea. The inner and outer cells make a triangle with a narrow base, which clings to the membranea basilaris; they turn somewhat outward. 1

A large oval nucleus lies in the basal part of each cell; that of the inner pillar cell is very large, about twice as large as that of the outer, and with its long axis in a radial direction. As figure 4 shows, the inner corner of the inner pillar cell does not yet reach to the habenula perforata.

The hair cells, which in the albino rat are in four rows through all the turns, are separated by the pillar cells into two groups, the inner containing one and the outer three rows of cells. They are comparatively well developed at birth (fig. 4). The inner hair cell belongs to the greater ridge, as Kolliker ('67), Gottstein (72), Retzius ('84), Held ('09), and others have already affirmed, and contrary to the assertaion of Bottcher ('69) and others.

It is situated in the most outer part of the declivity of the greater ridge and slants away from the axis with its round lower end at about half the height of the greater thickening. It has a large round nucleus in the base and the small hairlet at the top. This hair cell is nearly twice as large as the outer hair cells. The three outer hair cells reach down to the middle of the lesser ridge, not through it, having no process at their basal end. They end with their upper parts at the surface of the prominence. They stand not straight, but turn with their long axis very slightly inward, i.e., the in direction opposite to the long axis of the inner hair cells. They are cylindrical in form with a round nucleus at their base and small hairlet on the top.

Below the outer hair cells stand the three rows of Deiters' cells, which have large oval nuclei. These rest with their wide bases on the basilar membrane and their pointed ends reach to the surface of the epithelium. They are retarded in development, and at birth their cell bodies are short and undeveloped, so that they hardly suggest the adult cells.

• 1 In the following description of the cochlea, 'outward' means away from the axis 'inward' towards the axis.

Hensen's supporting cells (fig. 10, at maturity) are as yet undeveloped and nearly uniform in height, their nuclei being at nearly the same level.

Outward from the Hensen's cells the height of the epithelial cells at maturity rapidly diminishes and passes over to the cylindrical cells of sulcus spiralis externus. At birth no such distinction is present. Through all the turns the surface of the lesser epithelial ridge remains about parallel to the plane of the membrana basilaris.

The membrana basilaris, which stretches from the labium tympanicum outward to the crista basilaris of the ligamentum spirale, consists of two layers, an upper, membrana basilaris propria, and an under, tympanic investing layer (tympanale Belegschicht : Retzius). The former, of course, is divided into two portions, an inner, zona arcuata (Deiters) and an outer, zona pectinata (Todd-Bowman). While the zona arcuata is thin from the beginning of life, the zona pectinata thickens at its central part where it contains cells with oblong nuclei. On passing to the spiral ligament it again becomes thin. In the young, the under layer is not so regular in structure as in the adult. The *cells close to the basilaris propria are arranged vertically.

Figs. 4 to 12 Showing the increase in size and morphological changes in each part of the tympanic wall of ductus cochlearis of the cochlea during growth, in the radial vertical section albino rat. All the figures have been uniformly enlarged.

Fig. 4 One day. C, greater epithelial ridge; L, lesser epithelial ridge.

Fig. 5 Three days.

Fig. 6 Six days.

Figs. 7 to 8 Showing the differences in size and morphological changes in the tympanic wall of ductus cochlearis between a nine-day-old rat which can already hear (fig. 8) and one that cannot (fig. 7)

Fig. 9 Twelve days.

Fig. 10 Twenty days. In figure 10 we have drawn all the elements of the organ.

ABBREVIATIONS

M.T., membraua tectoria a. Corti O.P., outer pillar

L.V., labium vestibulare of crista B.C., basal cells

spiralis D.C., Deiters' cells

S.S.I., sulcus spiralis interims Bo.C., Boettcher's cells

S.I.C., cells of sulcus spiralis interims L.S., ligamentum spirale

I.S., inner supporting cells N.F., myelinated fibers of ramus I.H., inner hair cells acustici

O.H., outer hair cells R.F., radial fibers of ramus basilaris H.S., Hensen's supporting cells acustici in the tunnel of Corti

S.E.C., cells of sulcus spiralis externus T., tunnel of Corti

M.B., membrana basilaris B., blood vessels

I. P., inner pillar 0., bone

Fig. 1 1 One hundred days.

Fig. 12 546 days.

On the contrary the cells below them, which vanish in great part with age, have an irregular arrangement; those near the endothelial cells of scala tympani having a more radial arrangement. Therefore, this layer is thick, several times the thickness of the basilaris propria, and the thickness increases towards the upper turns. The vas spirale is strikingly large at this stage and lies just under the outer pillar and the Dieters' cells.

The membrana tectoria, beginning at the inner angle of the ductus cochlearis, where Reissner's membrane rises, covers the epithelium of the limbus laminae spiralis and the greater epithelial ridge, lying close to their surfaces. At the inner part it is thin, but thickens where the greater ridge begins, and at the outer part again becomes thin. In the basal turn there is seen as a very thin strand reaching to Hensen's prominence, but in the apical turn it reaches hardly to the inner hair cell. Although it gives rise to several thread-like processes going to the surface of the papilla, these do not seem to connect with the hairs of the hair cells, but with the terminal plates of the Dieters' cells.

When we divide the tympanic wall of the ductus cochlearis at the boundary between the greater and lesser epithelial ridges, we observe that the inner portion from the inner angle to the outer end of the greater ridge is far larger than the outer portion, which, however, is the more important for hearing. This relation becomes more evident as we pass from the base to the apex. Moreover, the total radial length of the tympanic wall diminishes at this stage towards the apex, though it is larger in the beginning of the middle turn than in the middle of the basal turn. As will be shown later, these relations are entirely reversed in the adult cochlea. This fact indicates that the cochlea at this stage is very immature.

In the three-day-old rat the cochlea is much better developed (fig. 5). The radial breadth of the typmanic wall of the ductus cochlearis becomes greater in all the turns, especially in the upper turn; therefore the differences between the radial breadths in each successive turn are smaller than at the earlier stage. There is some change as we pass towards the apex in the relation of the inner and outer portion of the tympanic wall. At the basal turn and the beginning of the middle turn the radial breadth of the outer portion increases greatly, but diminishes again towards the apex. Although the radial breadth of the inner portion increases through all the turns, the proportion of this increase becomes greater towards the apex. As the inner portion is composed of the greater epithelial ridge and of the limbus laminae spiralis, and as the breadth of the latter diminishes towards the apex, the increase of the radial breadth of the inner portion is due to changes in the greater epithelial ridge.

The heights of the greater epithelial ridge, however, diminishes through the successive turns, becoming less and less from base to apex. Thus in the cochlea at this age it has a small radial breadth and vertical height in the basal turn and a larger radial breadth and height in the upper turns.

In all the turns the inner hair cell is inclined outwards and lies with its surface forming the outermost part of the greater ridge. The obtuse angle which it helps to make (fig. 5) as a boundary between the greater and lesser ridge in upper turns, vanishes in the basal turn where there is no sharp boundary between the two ridges.

The pillar cells of Corti develop more and more during this early stage; the radial breadth of their base increases, but as yet there is no space between them. They incline much more outwards than in the earlier stage. The protoplasmic change in the rod progresses, especially in the basal turn, and the head plate of the cell can be seen distinctly.

The outer hair cells become higher and wider; they are slightly inclined inward in the upper turn. On passing towards the basal turn the inclination inward increases, and in the basal turn it is most oblique, almost at 45, to the plane of the basilar membrane. In figure 4 the inclination of these cells is only slight.

Deiters' and Hensen's cells are not well developed; the conditions are as in the former stage.

The plane of the surface of the lesser epithelial ridge is intimately related to the development of the outer hair cells and Deiters' cells, and as the latter are in an undeveloped condition, it runs nearly parallel to the plane of the membrana basilaris, sometimes dipping outward.

The membrana basilaris seems to be much longer; its composition is about the same as that in the one-day rat, only the thickness is somewhat decreased, owing to the reduction of the rows of cells in the tympanic layer.

The membrana tectoria grows in breadth and thickness, covering very closely the inner portion of the tympanic wall and connects outwards with Deiters' and Hensen's cells by slender fibrous processes the so-called outer marginal zone. The hairs of the cells stand between these processes, but have no connection with them.

The vas spirale does not suffer reduction.

At six days (fig. 6) the development of the cochlea has proceeded futher. The radial breadth of the tympanic wall has increased. Thus we find the tympanic wall, especially its inner portion, increasing towards the apex, chiefly owing to the augmentation of the radial breadth of the greater ridge. In this a remarkable change is to be seen. In the basal turn the long slender cells disappear in the inner part of the greater ridge, and instead of them there are found cylindrical cells with oval nuclei near their bases.

The height of these cells increases gradually to the level of the surface of the inner hah- cell; their upper surface is here in contact with the membrana tectoria. Thus a space appears between the cylindrical epithelium and the membrane the sulcus spiralis interims which is deep and wide in the basal turn, becomes gradually shallow and narrow as we pass upward, and in the middle part of the middle turn is to be seen as a small and flat space. In the apical turn it is not yet present. The inner side of this space is made by the labium vestibulare of the limbus laminae spiralis.

As a result of this change in the greater ridge, the obtuse angle between the greater and lesser ridge vanishes entirely, and the two surfaces come to lie in the same place. The inner hair cell becomes larger and inclines less outward.

It is to be noted that the inner hair cell is supported on both sides by long slender cells. These have been variously described by several authors, but first Hans Held ('02) and afterwards Kolmer ('07) have considered them as supporting cells, reaching from the surface of the hair cell to the plane of the basilar membrane. Held has termed the cell which lies outward the ' Phalangenzelle. '

I have paid some attention to this cell and the changes in it. It is long and slender and stands between the inner hair cell and the inner pillar cell, with the upper end reaching to the surface, and is attached at its base to the inner corner of the inner pillar. The oblong oval nucleus lies in its basal portion. On the inner side of the inner hair cell there is a group of two to three cells of the same kind. These cells, termed ' Grenzzellen ' by Held, stand near the habenula perforata, reach to the height of epithelium, and have their bases in intimate relation to the former.

These are not neuro-epithelial cells nor in intimate relation with the nerve fibers, but similar to the Deiters' cells which support the outer hair cells.

The developing pillar cells become progressively wider at their bases. The inner pillar cell sends a long foot towards the habenula perforata and in the basal turn it sometines reaches to it. The outer pillar cell increases its length very rapidly and extends its foot outward on the basilar membrane. Thus in the basal turn the triangle made by the inner and outer pillar cells and having a short base, in the upper turns changes to an equilateral triangle and stands upright on the basilar membrane. In the apical turn the inner pillar cell is not yet so long as in the lower, turns and is still inclined outwards. The head plates and pillars are fairly prominent, but there is as yet no space between them.

The outer hair cells have grown and are inclined inward. Deiters' and Hensen's cells have not yet begun to develop, as have the other elements of the organ of Corti just described.

In the membrana basilaris we see the reduction of cells in the tympanic covering layer. The vas spirale shows more or less reduction. The membrana tectoria increases its radial breadth following the associated structures. The so-called marginal zone connects with Hensen's cells and the lamina reticularis by fibrous processes.

Among five nine-day-old rats, as shown later, one responded to the tests for hearing. As the majority of them gave no reaction, the cochlea of the latter, non-hearing rat, may be taken as the type for this age. The differences between the cochlea of the hearing and non-hearing rats will be mentioned later.

In rats of this age (fig. 7.) the cochlea is still further advanced. The sulcus spiralis internus appears through all the coils, and is deepest and broadest in the basal turn, diminishing in depth or gradually toward the apex. The cells covering the space are low and cuboid in the lower turns, but in the apical turn they are yet relatively high, cylindrical cells.

These cells probably have their origin from the long slender cells of the greater epithelial ridge, as Bottcher ('69) and others maintain, although Gottstein (72) and some others think that they come by the outward migration of the epithelium of the limbus spiralis, and Retzius ('84) regards this latter view as the more probable.

The inner and outer hair cells become large and approach their mature form. The supporting cells of the inner hair cell are very evident.

The pillar cells develop more and more, their radial breadth increases and the pillars and headplates also become distinct. Sometimes we see a small space between the inner and outer pillar cells in the lower turn, but not in the upper. Nuel 's space is not yet to be seen. Deiters' cells become longer, somewhat in the processus phalangeus but chiefly in the cell body, and the nuclei move upward. Hensen's cells also increase in height slightly.

While the membrana tectoria lies close to the surface of the outer part of the greater ridge in the upper turns of the cochlea, there arises a small space between them, which is continuous with the sulcus spiralis internus. The outer marginal zone of the membrane is still connected with Hensen's supporting cells and the lamina reticularis. The vas spirale remains as a large vessel. This is the condition of the nine-day cochlea in a rat which does not hear.

Although the detailed description of the cochlea of the nineday rat which can hear will be deferred for a time, yet to complete the series of growth changes, figure 8, representing the cochlea in such a rat, is inserted here.

In the next stage, twelve days old (fig. 9), the development of the tympanic wall is much advanced. The cells lining the sulcus spiralis internus and the-inner supporting cells have nearly their mature form and arrangement in the basal and middle turns; only in the apical turn many and slender cells remain close to the inner hair cell.

The outer pillar cell shows a remarkable increase in length so that it is twice as long as in the former stage, while the growth of the inner pillar is much less marked.

Therefore the outer pillar is much longer than the inner through all the turns. From this change in the pillar cells it results that the nearly equilateral triangle formed by them becomes unequal and its summit is shifted inward. In all the turns we can see the tunnel of Corti and also the space of Nuel. The hair cells develop further and their previous inclinations are increased.

Deiters' cells show a very rapid development, especially in the cell body, which increases many times, the nucleus moving upwards. The inclination of these cells follows that of the outer hair cells.

Hensen's supporting cells are also fully developed. Through the development of Deiters' and Hensen's cells a change is effected in the course of the lamina reticularis. It runs no longer parallel to the plane of the membrana basilaris, but dips inward.

Though the membrana basilaris remains nearly stationary in its breadth, the thickness of the tympanic covering layer is reduced and the longitudinal nuclei in the zona pectinata diminish in number.

The membrana tectoria reaches in the basal turn to the outermost row of the outer hair cells, but the apical turn only to the second row. The so-called 'outer marginal zone' connects with the terminal frame (Schlussrahmen) of the lamina reticularis.

In the next stage, the twenty-day-old rat (fig. 10), the papilla spiralis and the tissues about it are developed almost completely; therefore, the structural relations of the cochlea accord nearly with those of the adult cochlea, as generally recognized in histology.

It is to be noted here that in the basal turn, Bottcher's cells are to be seen in sulcus spiralis externus* as a cell group situated on the outer part of the vestibular surface of the membrana basilaris. This cell group consists of several granular compact and sharply bounded cells entirely covered by high swollen cells on all sides. That this cell group belongs to the epithelium of the sulcus spiralis externus can be easily demonstrated. While the cells in this group show no particular changes in structure, the neighboring cells diminish in their height and size towards the apex, and finally become similar to the former. After twenty days of age the general features of the cochlea are those of the adult and do not require general description. The finer differences will be discussed in subsequent chapters.

Figure 11 shows the relations at 100 days and figure 12 at 546 days.

1. Membrana tectoria

As stated above, this membrane is divided into two zones, an outer and inner, using the outer edge of the labium vestibulare as the point of division (fig. 1, 7-7'). Each zone was again divided into two equal parts at 6-6'and8-8'. Thus the sum of the breadths of the two outer parts represents in each instance the breadth of the outer zone, and the sum of the two inner parts that of the inner zone, while the sum of all four parts gives the total radial breadth. For the purpose of the exact measurement of the growth of the membrane, I have, as noted above, projected the sections at 100 diameters and made the determinations on the outlines thus obtained.

In table 4 (charts 2 and 3) are given the values for the total average breadth, as well as for that of each zone, and also the thickness of the membrane, from 1 to 546 days of age. At the bottom of each column are given the ratios of the breadth at 1 to 546, 12 to 546, and 20 to 546 days. While the ratio between 1 and 546 days is 1.7, those from 12 to 546 days and 20 to 546 days diminish to about 1:1.0, that is the membrane at twelve days has attained about its full breadth, and there is only a very gradual increase in its breadth with advancing age. After twelve days similar ratios are found for the separate zones as well.

From 1 to 546 days the ratios for the two zones differ considerably; that for the second zone is 1:1.2 and that for the first is 1:3.6. This is due to the fact that in the cochlea at birth the development of the labium vestibulare is incomplete, even in the basal turn, while at the apex we can very often hardly see the invasion of the mesenchymal tissue in the inner part of the greater epithelial ridge.

At every stage the outer zone is broader than the inner; the ratio between them at birth is 1:3.8. This diminishes to 1:1.25 at twelve days, after which age it remains practically constant. Owing to the form of the membrana tectoria and to its great sensitiveness to the method of preparation, it is difficult to obtain good values for its thickness.

Generally speaking, the membrane is thickest about midway between the outer edge of the labium vestibulare and the inner boundary of the inner hair cell, and it was here the measurements given in table 4 were made. As shown in this table, the thickness increases rather rapidly from birth to twenty days, but after that period remains approximately constant.

As we know, the radial breadth of the membrane increases gradually from the basal to the apical turn. Table 5 (charts 4, 5, and 6) shows how the breadth of the total and of each part of the membrane changes in successive turns from base to apex according to age. At birth it is broadest in the beginning of the middle turn (turn II) decreasing gradually towards the apex. From three to twenty days the greatest breadth is usually found

TABLE 4

Average radial breadth of the membrana tectoria and its thickness in radial-vertical section. Averages of all four turns (charts 2 and 8)

AGE

BODT WEIGHT

BODY LENGTH

Outer zone between free end of membrane and labium

Inner zone labium vestibulare and insertion of membrane

Total length of membrane

Ratios inner and outer zone

Thickness membrane

days

grams

mm.

M

M

M

M

1

5

48

140

37

177

1 3.78

12

3

8

56

134

94

228

. 1.43

32

6

11

63

154

105

259

1.44

32

9

10

58

158

123

281

1.28

27

12

13

60

157

126

283

1.25

25

15

13

75

160

124

284

1.29

28

20

29

95

162

129

291

1.26

38

25

36

104

162

128

290

1.27

34

50

59

125

162

131

293

1.24

35

100

112

159

162

132

294

1.23

36

150

183

190

161

131

292

1.23

32

257

137

175

163

129

292

1.26

38

366

181

191

162

131

293

1.24

35

546

255

213

163

132

295

1.23

34

Ratios 1 546 days

1 1.2

1 3.6

1 1.7

1 2.8

t 12 546 "

1.0

1.0

1.0

1.4

20 5 "

1.0

1.0

1.0

0.9

in turn III, but after this in turn IV. At the bottom of each column are given the ratios of the radial breadth in each turn between the several age limits.

These show that after twelve days there is but little change in the radial breadth of the entire membrane in any turn.

On examining the growth in each zone of the membrane through the several turns, we find that after three days the outer zone of the membrane becomes at each age always broader from base to apex.

31

u

200

150

100

50

o

AGE QAYSH i i

O

25

50

5O 10O 2OO 3OO 4OO 50O

Chart 2 The radial breadth of membrana tectoria, table 4, figure 1. Total radial breadth of the membrane.

Radial breadth of outer zone.

• - Radial breadth of inner zone.

25 50 50 10O 2OO 3OO 4OO 5OO

Chart 3 The thickness of membrana tectoria, table 4.

32

ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

ta o

i < -S

a

2 S BS

.

n w

it

T^cOTtiCO-'^ -HOOOOOO

o; (

o;^ ^-^

(N 00

OOOOOOOO

co o !o

rH O

rH O

>> ^

c3

1 O I

rH'HCScouv.S "3:uj W i i ' co

20-546

GBOWTH OF THE INNER EAR OF ALBINO RAT

33

The values at birth are relatively greater than those at three days, as noted above, due to the undevelopment of the labium vestibulare. The inner zone grows in a like manner in breadth, but not so rapidly as the outer zone, and hence its relative breadth diminishes gradually from base to apex.

Table 6 shows these relations. While the ratios in the inner zone decreases from base to apex, those in the outer zone increase. Thus the ratios in the inner and outer zones according to the turns go in opposite directions. As stated above, the radial breadth is generally larger in the outer zone, but this relation is, in general, reversed in turn I, table 5.

TABLE 6 Condensed Ratios of the radial breadth of each zone of the membrana tectoria

Ratios according to turns of the cochlea

Ratios between inner and

BOOT

INNER CONE

OUTER ZONE

outer zone

AGE

__ fjfi**T

Turns

Turns

Turns

I-II

I-III

I-IV

I-II

I-II I

I-IV

I

II

in

IV

days

grams

1

5

1:0.8

1:0.5

1:0.0

1:1.2

1:1.3

1:1.4

1:1.8

1:2.8

1:4.3

1:0.0

8

11

0.9

0.9

0.8

1.4

1.8

1.9

0.8

1.2

1.6

2.0

18

21

0.9

0.9

0.8

1.4

1.8

2.0

0.8

1.1

1.5

1.9

203

160

0.9

0.9

0.8

1.4

1.7

2.0

0.8

1.1

1.5

1.8

In turn I the average ratios are, after eight days, smaller than 1.0; therefore, the inner zone is wider than the outer in turn I. It increases in all ages from turn II toward the apex.

In table 7 are given the ratios between each turn of the cochlea. The ratios after nine days of age are practically constant according to age, but those between turns I and II are always smaller than the others; the ratios for the two latter being alike. The ratio at one day is, however, an exception, as stated already.

As the measurements show, the membrana tectoria is at birth relatively undeveloped; it is thin and immature. After birth it increases rapidly during the first nine days, a statement which applies generally to the postnatal growth of the organs of the albino rat. Thus we get a ratio of the radial breadth 1 :1 .7 between 1 and 546 days, but after twelve days the ratios remain practically 1:1.0. (Table 4.)

ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

It is not my purpose to describe the fetal development of the membrana tectoria, but it is worth while to consider briefly the zones which compose the membrane; in other words, the parts of the tympanic wall from which it originated. There are chiefly

TABLE 7

Ratios of the radial breadth of the membrana tectoria according to the turns of the

cochlea

AGE

BODY WEIGHT

Ratios according to turn of the cochlea

I-II

I-II I

I-IV

days

gms.

1

5

1 1.0

1 1.0

1 :0.9

3

8

1.2

1.2

1.2

6

11

1.2

1.4

1.3

9

10

1.1

1.3

1.3

12

13

1.1

1.3

1.3

15

13

1.1

1.3

1.3

20

29

1.1

1.3

1.3

25

36

1.1

1.3

1.4

50

59

1.1

1.3

1.3

100

112

1.1

1.3

1.4

150

183

1.1

1.3

1.3

257

137

1.1

1.3

1.3

366

181

1.1

1.3

1.3

546

255

1.1

1.3

1.3

Chart 4 The total radial breadth of membrana tectoria arranged according to the turns of the cochlea, table 5.

About middle part of the basal turn (I).

About the beginning of the middle turn (II).

About the middle part of the middle turn (III).

About the beginning of the apical turn (IV). 2

Chart 5 The radial breadth of the inner zone of the membrana tectoria,

according to the turns of the cochlea, table 5.

Chart 6 The radial breadth of the outer zone of the membrana tectoria,

according to the turns of the cochlea, table 5.

• In most cases when the values which have been determined are analyzed

according to the turns of the cochlea, it is found that they increase with later growth from the basal (I) to the apical (IV) turn and in the order just given in chart 4. Owing to this uniformity of behavior, some thirteen charts showing the several values according to turn have been omitted, since the graph given by the average value is sufficiently informing in each instance.

In the case of those charts which have been retained, and in which the measurements are according to the turns of the cochlea, the respective turns I-IV are recorded by characteristic lines similar to those used for them in chart 4, and in these cases the further designations of the turns are omitted.

350

300

I

ISO

G.E DAYSH

25 5O

50 1OO 2OO 30O 400 500

Chart 4

150

1OO

50

AGE

25 50 50 1OO 200 300 4OO 500

Charts

180

100

DAYS

25 50 5Q 1OO 2OO 3OO 4OO 5OO

Chart 6

36

two views about this. While a few authors, Kolliker ('67), Hensen ('63), and recently Hardesty ('08, '15), and others hold that only the greater epithelial ridge takes part in the formation of the membrane, most investigators (for example, Bottcher, '69; Retzius, '84; Rickenbacher, '01; Held, '09; Van der Stricht, '18) consider that it originates from both the greater and lesser epithelial ridge. My figure 5, supports the latter view; that is, while the main part is developed from the greater ridge, the outer narrow marginal part is secreted from the lesser ridge.

The figure in Quain's Anatomy by Schafer ('09) (vol. 3, part 2, p. 332, llth ed.,) is from the earlier paper of Hardesty and shows the membrane in the pig as arising from the greater epithelial ridge only.

Hardesty has corrected this figure in his paper published in 1915. Thus in the very early stage after birth in these forms we have three zones, an inner, an outer, and a marginal zone. With age, however, this marginal zone becomes, as Held ('09) and others agree, gradually smaller and smaller, and finally it is difficult to differentiate it from the outer zone. Thus for convenience in measurements I have treated the membrane as consisting of two zones only.

Comparing the breadth of the inner and outer zones, it is evident that the outer is always the broader. The ratio is (table 4) at birth 1 : 3.78, at three days 1 : 1.43, and then gradually diminishes to 1:1.23 with age.

Now if we examine the ratios of the total breadth of the membrane according to the turns of the cochlea, we find after six days that the ratio generally increases from base to apex, and that these ratios remain nearly constant after nine days of age, as shown in table 7.

Thus the ratio between turns I and II is 1:1.1; between turns I and III, 1:1.3; between turns I and IV, 1:1.3. The breadth of the membrane increases, -therefore, in the albino rat gradually from the base to the middle part of the middle turn; from this point it does not increase to the apex.

Since the breadth at the tip of the apex diminishes greatly, as is generally recognized, Hardesty ('08) found in the pig the following ratios (table 8):

GROWTH OF THE INNER EAR OF ALBINO RAT

37

Comparing these ratios obtained by Hardesty in the pig with mine, there appear to be large differences between them. The reason for these I will discuss later.

When we consider the breadth in each part of the membrane according to the turn, we find that the increase of the breadth of the membrane in each turn is due to the development of the outer zone. The inner zone, which is adherent to the labium vestibulare, does not increase in the rat as Hardesty ('08/15) found to be the case for the pig, but on the contrary decreases from base to apex a relation found by Retzius ('84) in the rabbit, cat, and man and confirmed by Rickenbacker ('01) in the guineapig. On the contrary, the outer zone increases in breadth from

TABLE 8 Ratios of the breadth of the membrana tectoria according to turn of cochlea (Hardesty)

Kind of animal

Preparation method

Ratios between breadth in 7 and 5 half turn

Ratios between 7 and 3 half turn

Ratios between 7 and 1 half turn

Pigs two weeks of age

Membrane teased out Membrane

1 : 1.4

1 :1.7

1 :2.5

teased out

1 :1.8

1 :2.5

1 :2.7

Adult

Membrane in

section

1 : 1.6

1 :2.1

1 :1.8

base to apex, and in each stage the ratios between the successive turns are nearly the same. These ratios between successive turns, however, show rather large differences according to the different authors.

My results (table 5) show that the outer zone in the albino rat is nearly two times wider at the apex than at the base. This agrees with what von Ebner ('02) finds in the human cochlea.

When we consider the thickness of the membrane, we find it thin at birth, but at three days (table 4) it increases rapidly and reaches almost its greatest thickness. This increase in thickness arises through the apposition of new layers to the under surface, as Hasse (73) and others have noted, but very large differences appear between the figures given by various authors.

38 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

Kolliker ('67) finds the membrane 45 n thick in the ox. In the guinea-pig it is 15 ^ in the thickest place, according to Schwalbe ('87). Middendorp ('67) gets in mammals generally a very thin membrane, about 1 n thick. Retzius ('84) states that in the thickest part in the rabbit it measures 27 [x, in the cat 32 to 50 |x, and in man 24 to 25 [x. Hardesty finds in the young pig an average thickness of the teased membrane of 50 [x and in an adult hog 119.3 (x. I get 35 (x as an average in the adult albino rat after twenty days of age, varying from 32 to 38 [x. My result is therefore closest to that for the cat as obtained by Retzius. These results are plainly influenced b.y the dissimilar technical methods used by the several investigators.

About the outermost end of the membrane there are still two different views. One view is that the outer end of the membrane projects beyond Hensen's prominence; Kolmer ('07; pig, calf goat and horse); Hardesty ('15; pig, hog) Shambaugh ('10; pig). Others assert that the membrane terminates with its outer edge at the outer boundary of the outermost series of the outer hair cells. My preparations show that in the rat the outer end of the membrane does not reach Hensen's prominence.

Possibly this difference is due to the technique of preparation. In the figures drawn by many authors we can recognize many artifacts and postmortem changes in the cochlea. Even in the figures of Kolmer ('07) we see these changes, although he injected the fixing solution through the carotid artery. Held ('09) says in his criticism of Hardesty 's figures that " figures 6 and 7 wie schon Hardesty selbst vermutet hat, sicherlich auf einer Verquellung beruhen "

I myself never observed such a gigantic membrane as Hardesty ('08, '15), Shambaugh ('10), and others show in the cochlea of the pig. On the other hand, I cannot absolutely deny that there may have been shrinkage in the cochleas prepared by my methods, though I see no evidence of it.

From our present knowledge, however, the method of vital fixing is considered the best available, as already maintained by Siebenmann and Yoshii ('08), Metzner and Yoshii ('09), Nager and Yoshii ('10), Wittmaack and Laurowitsch ('12), and others.

By using this vital-fixation method we get perfect sections which can be used to solve the problem of the shifting of the organ of Corti an event which I will discuss later.

2. Membrana basilaris

The membrana basilaris of the cochlea stretches between the limbus laminae spiralis and the ligamentum spirale. The acoustic terminal apparatus is situated on it and according to the dominant Helmholtz-Hensen theory, this membrane is to be considered as very important in tone perception. The row of the fine holes, foramina nervina, is generally designated as the inner boundary of this membrane. Strictly speaking, however, the beginning of the membrane is at the outer edge of the labium tympanicum, which sharpens at first beyond the foramina nervina and passes over to the substance of the membrana basilaris. Practically it is almost impossible to decide exactly the point of transition. Thus I have used in the measurement of the membrane the foramina of the habenula perforata as an inner limiting line following in this Retzius, ('84) Schwalbe ('87), and others. Here it is to be mentioned that the organ of Corti lies with its inner portion not only upon the inner part of the membrane, but extends to the foramina nervina also.

The membrana basilaris is usually divided into two portions; the inner, termed the zona arcuata, and the outer, the zona pectinata. The former stretches from the habenula perforata across the base of the tunnel of Corti to the outer edge of the foot of the outer rods of Corti ; the latter extends from this point to the ligamentum spirale (fig. 2), 5= inner zone, 10= outer zone.

In table 9 (chart 7) are given the values for the total radial breadth of the membrane, that of each zone, and the ratios between them. At the bottom of each column are given the ratios at 1 to 546, 12 to 546, and 20 to 546 days of age. In the total radial breadth of the membrane, as the table shows, there are large differences on age from birth to nine days. Between 1 day and three days the increase is 30 |x and between three days and six days, 28 [A. After nine days the breadth increases more slowly but continuously to old age.

In the growth of both zones we see about the same relation. These increase rapidly from birth till nine (or twelve) days and after that very slowly. These relations are shown clearly in the ratios at 1 to 546, 12 to 546, and 20 to 546 days. While after twelve days the ratios in total breadth and in each zone are the same, 1:1.1, that for 1 to 546 days is smaller for the outer zone than it is for the inner zone, thus the inner zone increases considerably after birth, while the outer zone does not grow, as some authors have imagined, as much as the inner zone. I will discuss this point later.

Online Editor - TABLE 9 (to be formatted)

TABLE 9 Radial breadth of Ihe membrana basilaris measured between the foramina nervina and ligamentum spirale in radial sections on age (chart 7, fig. 2} AGE BODY WEIGHT INNER ZONE (Zona arcuata) OUTER ZONE (Zona pectinata) Total radial breadth of the membrane Ratios between the radial breadth of the inner and outer zone days grams P M M M 1 5 49 75 124 1 1.5 3 8 63 91 154 1.5 6 11 77 105 182 1.4 9 1 10 79 111 190 1.4 12 13 - 88 100 188 1.1 15 13 87 102 189 1.2 20 29 86 106 192 1.2 . 25 36 87 108 195 1.2 50 59 88 107 195 1.2 100 112 92 106 Id8 1.2 150 183 92 107 199 1.2 257 137 92 107 199 1.2 366 181 93 111 204 1.2 546 255 94 113 207 1.2 Ratios 1 546 days 1 1.9 1 1.5 1 1.7 12546 " 1.1 1.1 1.1 20546 " 1.1 1.1 1.1 1 A rat of nine days which could hear, gave the following: Right side 11 94 103 197 91 104 195 93 104 196 1 : 1.1

Comparing the growths of the radial breadth of the inner and outer zones, we find that the inner zone is relatively narrow at nine days; thus the ratios between them are 1:1. 4; after that period the inner zone increases rapidly, and even at twelve days the ratio becomes 1:1.1, which is almost the same as in the adult, 1:1.2.

In table 10 the radial breadths of the whole membrane and of its zones are arranged accordingly to the turns of the cochlea on age. At the bottom of each column are given the ratios from 1 to 546, 12 to 546, and 20 to 546 days. We see at first that the total radial breadth at one day is largest in the basal turn; at three days it becomes larger on passing from the basal toward the II and III turns, but in turn IV it is again small.

Chart 7 The radial breadth of the membrana basilaris, table 9, figure 2, distance 11.

Total radial breadth of the membrane.

Radial breadth of the zona pectinata.

Radial breadth of the zona arcuata.

After six days it is a well-known fact that the radial breadth of the membrana basilaris is narrowest in the basal, and widest in the apical turn (not the tip of the apex, but the beginning of the apical turn). These differences are not always the same between all the turns; those between I and II, and II and III are marked; those between III and IV are small. The ratios at 1 to 546 days show those for the upper turn to be largest, while from 12 to 546, and 20 to 546 days the ratios in all turns are about 1:1.1.

In the zona arcuata (inner zone) the same relation is to be seen in each turn; therefore, in the early period the breadth is less in turn IV than in the other turns. Very soon, however, the value in turn IV becomes the largest and diminishes toward the base. The rate of the growth of this zone, from 1 to 546 days, is also smallest in turn I, and largest in turns III or IV; the ratios being in the first 1:1.6, and in the last 1:2.1.

In the zona pectinata (outer zone) we see also similar relations.

Online Editor - TABLE 11 (to be formatted)

TABLE 11 Ratios of the radial breadth of the membrana basilaris according to the turns of the cochlea on age AGE BOOT WEIGHT Ratios between turns I-II I-III I-IV days gms. 1 5 1 1.0 1 1.0 1 1.0 3 8 1.0 1.0 1.0 6 11 1.1 1.2 1.2 9 10 1.1 1.2 1.1 12 13 1.2 1.3 1.3 15 13 1.1 1.3 1.3 20 29 1.1 1.2 1.3 25 36 1.2 1.3 1.3 50 59 1.1 1.3 1.3 100 112 1.1 1.3 1.3 150 183 1.1 1.2 1.3 257 137 1.1 1.2 1.3 366 181 1.1 1.2 1.3 546 255 1.1 1.2 1.3

Only slight differences in the ratios according to age are found.

In table 11 the ratios according to the turns of the cochlea are given. While from one to three days the ratios are the same in each turn, 1:1.0, yet after six days those for turns I to II are smallest, and for I to IV larger, thus showing slight differences between them.

In the literature we find only one description, that by Retzius ('84) touching the growth of the radial breadth of the membrana basilaris according to age. He measured this membrane in the rabbit and cat and got the following values in n (table 12).

Comparing these values with mine obtained for the albino rat, it is to be noted that those of Retzius are generally larger than those for the albino. For example, while I get at birth only 126 (x in the basal turn, Retzius ('84) obtains 180 [x in the rabbit and even 270 [x in the cat. As stated above, the radial breadth increases in the albino rat continuously with age. It is very peculiar to find in the Retzius table that the breadth of the membrane in the cat is decidedly larger at birth than at three and seven days. The average value for the new-born is 315 [x, which is larger than at thirty days, which is 310 [x.

Retzius ' data show the membrane in the rabbit and cat always wider in the apical than in the basal turn at birth and at two days. My results, given in table 10, show the reverse at the ages of one and three days. This is an expression of greater immaturity in the case of the rat.

Online Editor - TABLE 12 (to be formatted)
TABLE 12 Breadth of membrana basilaris according to turns, p. (From Retzius, '84} RABBIT CAT Age Basal Middle Apical Basal Middle Apical days New-born 180 270 270 300 375 2 220 272 280 3 . 200 280 7 270 306 211 258 300 10 255 310 390 11 255 300 330 14 300 360 410 30 240 300 390

In comparisons like the foregoing, several conditions must be kept constantly in view.

So far as absolute values are concerned, it is to be expected that these would be unlike in the different mammals, because the cochleas differ in size. As to the relations between the values at birth and at maturity, it is plain that these cannot be expected to agree unless the cochleas of the animals compared are in the same phase of development at birth. In the foregoing instances it appears that the cat is relatively precocious, as compared with the rabbit, while, as might be expected, because of their closer zoological relationship, the rat and the rabbit are in better agreement, although the rabbit appears to be a trifle more advanced at birth than the rat.

Finally, in the comparison of different series of data, differences due to the lack of homogeneity in the series of animals used and to the various techniques employed can hardly fail to play an important part, and allowance must be made for these disturbing factors.

When we consider the rate of growth, the ratio of a one to a fourteen-day-old rabbit is 1:1.6, according to Retzius; therefore, it has very nearly the value found in the albino. In the cat, however, the ratio between one and thirty days is 1:0.97; therefore, it apparently decreases a bit.

This difference is most readily explained as due to the precocious development in the cat at birth.

On comparing the radial breadth of the membrane obtained from several mammals by various authors, we find the following values (table 13).

Online Editor - TABLE 13 (to be formatted)
TABLE 13 Breadth of basilar membrane ANIMAL AUTHOR TURN IN WHICH MEASUREMENT WAS MADE IN M Basal Second Third Fourth Average Man-New-born Hensen ('63) 235 413 495 381 Man Mature Retzius ('84) 210 340 360 303 Calf Kolmer ('07) 200 280 400 293 Pig Kolmer ('07) 168 200 256 304 232 Goat Kolmer ('07) 124 384 432 313 Cat Bottcher ('69) 90 435 263 Cat Middendorp ('67) 246-275

The values here given must be read in the light of the various modifying conditions to which reference has just been made.

My average value after twenty days is 199 [i; therefore, it is absolutely the smallest in this series of mammals. The rat is also the smallest species examined.

As shown in the literature quoted, and also in my own results, the membrane increases in its breadth in all the mammals examined from the base toward the apex a relation contrary to that reported by the older authors (Corti, '51, and others). This increase is continuous, but is at first more rapid and afterwards more gradual. The ratios of this increase in the albino rat are given in table 11.

The next question relates to the breadth of each zone of the membrane according to age. So far as I know, there is no such study in the literature, not even in Retzius. In the albino rat, as shown in table 9, each zone increases in breadth with age. The rate of growth, however, is somewhat different, and in the zona arcuata it is greater than in the zona pectinata (1:1.9 and 1 :1.5, respectively), although the absolute value is always greater in the latter.

As noted above, the membrane increases in its radial breadth from the basal to the apical turn. How, and in which portion of the membrane does this increase arise? Henle ('66) first regarded the breadth of the inner (zona arcuata) as approximately constant.

"Nicht nur in den verschiedenen Regionen einer Schnecke, sondern, soviel ich sehe, selbst in den Sshnecken verscheidener Tiere und des Menschen; sie schwankt nur wenig um 0.01 mm." (Eingeweidelehre des Menschen, 1866, S. 793).

In the second edition of his book ('73) he states, however, that in the increase of the breadth according to the turn, both zones seem to take part. Hensen ('63) gets in the zona arcuata of the base of the human cochlea the breadth of 19 ^ and in the apex 85 \L. Middendorp ( '68) gives in the cochlea of the cat a continuous increase of the breadth of the zona arcuata from 94 to 122.5 {A. .""'

More detailed data are given in table 14.

According to all these authors, the breadth of both the inner and outer zones increases from base toward apex and results in the increase of the total radial breadth of the membrane according to turn. My results obtained from the albino rat agree with these data.

3. Radial distance between the habenula perforata and the inner corner of the inner pillar cells at base

The measurements of the radial distance from the habenula perforata to the bases of the inner and outer pillar cells were taken to determine their postnatal growth. As already stated, the cells from which the arch of Corti arises stand at birth nearly vertically and have no space between them (fig. 4). In the adult, however (fig. 10), we see a space, the tunnel of Corti lying between them and changes in the form of the arch occur. To follow these changes it seems at first necessary to study the growth of the pillar cells and of the other elements in the organ of Corti. At the same time we must take into consideration the inward shifting of the organ of Corti, first studied by Hensen. This shift inward of the organ is, according to Hensen, chiefly caused by the wandering of the pillar cells, especially the inner pillar cell. Therefore, it seemed necessary to determine the radial distance of the pillar cells from the habenula perforata at different ages before discussing this interesting problem.

Online Editor - TABLE 14 (to be formatted)
TABLE 14 Breadth of the inner zone of the membrana baeilaria in n NUMBER Of TURN First Second Third Fourth Cat-adult Bottcher ('69) 60 105 135 Guinea-pig Winiwarter (70) 45-52 63-68 71-80 80-83

In table 15 are given the values for the radial distances between the habenula perforata and the inner corner of the inner pillar cell at its base according to age (figs. 4 to 9). As we see, the average value increases till three days of age, then vanishes suddenly, though at six days we have a measurable interval in the upper turns of the cochlea. Comparing these distances according to the turn, they are smallest in turn I and increase toward the apex. In some cases, at six days, we have no interval in the basal turn, but in the higher turns an interval gradually appears and at the apical turn is largest. This table shows, therefore, that the inner corner of the base of the inner pillar cell lies at birth outward from the habenula perforata at an average distance of 22 \L. At three days of age the inner corner moves farther outward with the developing membrana basilaris and the distance increases from the base to the apex. Between three to six days this outward movement not only stops, but reverses its direction, and at six days it often becomes zero in the basal turn. Bottcher ('72) finds in the cat the following values for this interval in \i (table 16).

Online Editor - TABLE 15 (to be formatted)
TABLE 15 Condensed Radial distance between the habenula perforata and the inner corner of the inner pillar at base on age AGE BODY WEIGHT TURNS OF THE COCHLEA M I II ill IV Aver. days 1 5 19 22 22 23 22 3 8 23 28 28 30 27 6 11 In one case 5 In 2 cases 10 14 18 In other 3 cases In other cases 9 10 12 13

Online Editor - TABLE 16 (to be formatted)
TABLE 16 CAT EMBRYO 11 CM. LONG ADULT CAT I II ill IV Average I II ill IV Average 15 39 30 30 29 3 3 3 3 3

Online Editor - TABLE 17 (to be formatted)
TABLE 17 RABBIT CAT AGE Basal turn Middle Apical Average Basal Middle Apical Average days New-born 300 300 300 300 5 40 45 30 2 10 12 30 17 3 3 36 7 11 18

Retzius ('84) studied this distance in the rabbit and cat and gets the values given in Table 17.

Comparing the values of these two authors with my own, there are of course some differences. While in the rabbit the interval is large at one day, it is greatly diminished at two days of age. At three days the inner corner of the cell reaches the habenula perforata. In the cat the values are nearer to mine. The fact that the values increase from base toward apex is to be seen here also. This peculiar phenomenon appears, therefore not only in the albino rat, but also in the rabbit and the cat during the earliest stage of postnatal life.

4. The radial distance between the habenula perforata and the outer corner of the inner pillar cell (resp. the inner corner of the outer pillar cell) at base

This measurement is difficult. As we know, the inner and outer pillar cells in the albino are from birth till nine days of age in contact with each other along their whole length, and therefore they do not yet surround the space forming the tunnel of Corti. At about nine days, however, the tunnel appears while the cells remain in contact by their bases. It is almost impossible to determine the line of contact on the basilar membrane in my preparations. To get the radial distance between the habenula perforata and the outer corner of the inner pillar cell I have proceeded therefore as follows:

First, I have measured this distance directly up to nine days of age; after that this distance consists of the sum of the radial basal breadth of the inner pillar (not pillar cell) and the breadth of the inner basal cell on the basilar membrane. Since it is impossible to get the latter value directly in my sections, I considered that half of the radial distance between the outer corner of the inner pillar and the inner corner of the outer pillar would be equivalent to it.

Of course, I do not know whether the value of the sum of these two distances is at all ages, identical with the distance between the habenula perforata and the outer corner of the inner pillar cell at its base. I believe, however, that a systematic study of the growth of this distance will be significant.

In table 18 are given the values for the radial distance between the habenula perforata and the outer corner of the inner pillar at base up to nine days of age. As shown, these values, on the average, increase with age. The increase of this distance means that the base of the inner pillar cell spreads outward more and more.

When we consider this distance according to the coil of the cochlea, it is at birth about the same through all the turns (table 18; at three days it increases up to turn III, and in turn IV the value is the same at the apex as at the base. At six days the value in turn III is also largest, and next largest in turn IV. At nine days of age the same relations are to be seen.

Online Editor - TABLE 18 (to be formatted)
TABLE 18 Radial distance between the habenula perforata and the outer corner of the inner pillar at base on age TURNS OF COCHLEA M AGE BODY WEIGHT I II III VI Average days grams 1 5 40 41 39 39 40 3 8 48 49 50 48 48 6 11 38 45 58 53 49 9 10 44 46 56 53 50

In table 19 (chart 8) are given the values for the radial basal breadth of the inner pillar (not pillar cell) on age. At the bottom of the last column are the ratios from 6 to 546, and 20 to 546 days. As above noted, the rod can be followed at birth from the upper part to near the base of the cell (fig. 4). At three days (fig. 5), its base reaches the basilar membrane as a thin and slender thread, but we cannot measure its basal breadth accurately. During the next few days it increases in radial breadth rapidly, and at six days has the average value of 29 [/. (table 19). After nine days it decreases distinctly till twenty days, after which the value remains nearly constant. These relations are evident in the ratios. While the breadth at six days is about twice that at 546 days, that at twenty days has the same value.

According to the turn of the cochlea, the values from nine to fifteen days become gradually larger on passing from the base toward the apex. After twenty days, however, this relation vanishes, and the values become nearly the same through all

Online Editor - TABLE 19 (to be formatted)

TABLE 19 Radial basal breadth of the inner pillar on age (chart 8) day* 1 3 ti 9 12 15 20 25 50 100 150 257 366 546 Ratios 6 20 WEIOHT BODY TURNS OF THE COCHLEA M I II III IV Average grams 5 8 11 29 31 27 27 29 10 28 28 33 35 31 13 18 19 22 25 21 13 18 18 19 19 19 29 14 15 15 15 15 36 14 15 14 15 15 59 14 14 14 13 14 112 14 14 14 13 14 183 15 15 15 15 15 137 15 15 15 15 15 181 16 17 15 15 16 255 15 14 16 15 15 -546 days 1 :0.5 -546 "

Chart S. The radial basal breadth of the inner pillar (not pillar cell), table 19, figure '2, distance 3.

the turns. In table 20 the ratios of the turns I to II, I to III, and I to IV are given for three age groups (condensed from table

From the data given by Retzius ('84) we get the values in jx of the radial basal breadth of the inner pillar in the rabbit and cat as follows (table 21).

Comparing these values with my own, it is to be noted that Retzius' measurements in the rabbit agree perfectly at the earliest stage with those in the albino rat. Also we find in the rabbit at seven days values homologous with those obtained in the albino rat at fifteen days of age, only in the rat the breadth is absolutely greater. In the cat the values at seven days of age are about the same, or a bit smaller, than those in the albino rat. Here again the rabbit is a trifle more precocious than the rat, and the cat much more so.

Online Editor - TABLE 20 (to be formatted)

TABLE 20 Condensed Ratios of the radial basal breadth of the inner pillar according to the turns of the cochlea on age RATIOS BETWEEN TTTBN8 AGE BODY WEIGHT I-II I-III I-IV days grams 8 11 1 1.0 1 1.0 1 1.1 14 13 1.1 1.2 1.3 189 124 1.0 1.0 1.0 TABLE 21 Radial basal breadth of inner pillar in n (Retzius) BABBIT CAT Age Basal turn Middle Apical Average Basal Middle Apical Average days New-born 11 2 3 12 7 15 12 15 14 10 15 10 17 18 18 18 11 15 15 14 15 15 12 14 30 9 12 15 12

Table 22 (chart 9) shows the values for the radial distance between the outer corner of the inner pillar (not pillar cell) and the inner corner of the pillar (not pillar cell) at the base, on age. At the bottom of the last column are given the ratios from 6 to 546, 12 to 546, and 20 to 546 days. As just stated, the inner, and especially the outer rods, do not appear in the respective pillar cells at the earliest stage, the latter becoming evident a bit later than the former. After six days of age the distance between them can be determined.

Online Editor - TABLE 22 (to be formatted)

TABLE 22 Radial distance between the outer corner of the inner pillar and the inner corner of the outer pillar at base on age (chart 9) AGE BODY WEIGHT TURNS OF THE COCHLEA M I II III IV Average days grams 1 5 3 8 6 11 25 28 29 34 29 9 10 27 30 35 30 31 12 13 37 41 51 53 46 15 13 35 46 56 56 48 20 29 43 53 66 68 58 25 36 42 58 67 68 59 50 59 41 54 68 74 59 100 112 44 59 71 78 63 150 183 43 59 68 76 62 257 137 46 56 66 75 61 366 181 45 57 68 74 61 546 255 47 60 71 74 63 Ratios 6546 days 12546 " 20546 "

Chart 9. The radial distance between the outer corner of the inner pillar (not pillar cell) and the inner corner of the outer pillar (not pillar cell) at base, table 22, figure 2, distance 6.

As table 22 shows, this distance increases at first rapidly, then more slowly with age. This agrees with the growth of the membrana basilaris, as already noted. While the value at 546 days is over twice as large as at six days, it is but little larger than at twenty days, as the ratios show. Moreover, the distance increases from the base toward the apex rapidly up to turn

Online Editor - TABLE 23 (to be formatted)
TABLE 23 Condensed Ratios of the radial distance between the outer corner of the inner pillar and the inner corner of the outer pillar, at base according to turns of the cochlea on age RATIOS BETWEEN TURNS I-II i-m I-IV days grams 8 11 1 : 1.1 1 : 1.2 1 : 1.2 14 13 1.2 1.5 1.5 189 124 1.3 1.5 1.7

III and less rapidly to turn IV. This relation is more concisely presented in table 23. Retzius ('84) gives the value of this distance in the rabbit and the cat as follows (table 24).

The table 24 shows that there is no measurable distance between the outer corner of the inner pillar and the inner corner of the outer pillar at the very early stage in the rabbit, and this result is like that for the albino rat. Later the distance is larger in the rabbit than in the rat. The rate of increase of the values from the base to the apex is, however, similar in both forms. In the cat, on the other hand, there is already at birth a large distance between the pillars. The cochlea of the cat is therefore at this period more advanced in this character than that of the rabbit or rat, but in the cat also the distance tends to increase from the base toward the apex.

In table 25 (chart 10) are given the values for the radial distance between the habenula perforata and the outer corner of the inner pillar cell (resp. the inner corner of the outer pillar cell) at the base according to age. This table is derived from tables 18, 19, and 22. The values from one to nine days of age are from table 18. Those after twelve days consist of the sum of the values in table 19 plus the one-half of those given in table 22 (fig. 2 value for bracket 3 plus one-half the value for bracket 6).

Online Editor - TABLE 24 (to be formatted)
TABLE 24 Radial distance between the outer corner of the inner pillar and inner corner of the outer pillar in n (Retzius) RABBIT CAT Age Basal turn Middle turn Apical turn Average turn Basal turn Middle turn Apical turn Average turn days New-born 64 2 3 45 7 57 75 75 69 50 75 10 52 72 74 66 11 75 95 14 63 100 99 87 30 66 93 90 83

The values increase gradually after birth till nine days, when they reach a maximum, and then decrease, but increase again very gradually till old age. If this method of measurement is accepted, then the inner corner of the inner pillar cell lengthens inward at the base in the earlier stages. At the time when the inner pillar reaches the habenula perforata, the outer corner of the inner pillar has not yet moved inward, and thus the breadth of the base is largest. After the inward wandering of the inner pillar cell, the base diminishes a little in its breadth; then it increases slightly with advancing age.

When considered according to the turn of the cochlea, this measurement generally increases from the base to the apex, but more rapidly from turn I to turn III, and only slightly from turn III to IV. Table 26 shows this relation. While at birth the ratio is in all turns the same, 1 :1.0, at other ages it is always higher. Retzius ( '84) gives the results obtained from the rabbit and the cat as follows (table 27).

Online Editor - TABLE 25 (to be formatted)

TABLE 25 Radial distance between the habenula perforata and the outer corner of the inner pillar cell (resp. the inner corner of the outer pillar cell) at base on age. Derived from tables 18, 19 and 22 (chart 10) AGE BODY WEIGHT TURNS OF THE COCHLEA M I II III IV Average days grams 1 5 40 41 39 39 40 3 8 46 49 49 49 48 6 11 38 45 58 53 49 9 10 44 46 56 53 50 12 13 36 45 50 50 45 15 13 36 41 47 47 43 20 29 36 42 48 49 44 25 . 36 35 44 48 49 44 50 59 35 41 48 50 44 100 112 36 44 50 52 46 150 183 36 45 49 53 46 257 137 38 43 48 51 45 366 181 39 45 49 52 46 546 255 39 44 52 52 47 Ratios 1 546 days 9546 " 12546 " 20546 " 1.2 0.9 1.0 1.1 60 JLL 40 20

Chart 10 The radial distance between the habenula perforata and the outer corner of the inner pillar cell (resp. the inner corner of the outer pillar cell) at base, table 25, figure 2, distance 8.

Online Editor - TABLE 26 (to be formatted)
TABLE 26 Condensed Ratios of the radial basal distance between the habenula perfcrata and the outer corner of the inner pillar cell (resp. the inner corner of the outer pillar cell) at base on age according to the turns of the cochlea RATIOS BETWEEN TURNS AGE BODY WEIGHT I-I1 I-HI I-IV days gram* 1 5 1 1.0 1 :1.0 1 :1.0 8 11 1.2 1.4 1.3 18 21 1.2 1.3 1.3 213 138 1.2 1.S 1.4

TABLE 27

Distance between the habenula perforata and the outer corner of the inner pillar

cell in n (Retzius)

Age

Basal turn

Middle

turn

Apical turn

Average turn

Basal turn

Middle turn

Apical turn

Average turn

days

New-born

30

45

39

38

60

60

60

60

2

30

36

30

32

3

44

60

7

37

46

45

43

45

69(?)

65

60

10

39

52

48

46

11

60

66

75

67

14

40

54

51

48

30

60

60

At the earlier stage this distance in the rabbit is a little less than in the rat. Soon after, however, it becomes about the same. In the cat the values are generally larger than in the rat.

5. Radial basal breadth of the outer pittar cett (including the outer pillar)

The measurement of the radial basal breadth of the outer pillar cell is difficult. At the earlier stage, in which the inner and outer pillar cells are in contact with each other along

Radial basal breadth of the outer pillar cell (including the outer pillar) from one

to nine days of age

TURNS OF THE COCHLEA M

AGE

BODY WEIGHT

I

II

III

IV

Average

days

grams

1

5

10

9

8

8

9

3

8

15

16

15

12

15

6

11

26

28

28

33

28

9

10

26

30

30

35

30

TABLE 29 Radial basal breadth of the outer pillar on age (chart 11)

AGE

BOOT WEIGHT

TURNS OF THE COCHLEA M

I

II

III

IV

Average

days

grams

1

5

3

S

6

11

10

14

16

17

14

9

10

15

18

18

21

18

12 .

13

14

23

25

22

21

15

13

17

21

23

20

20

20

29

13

13

16

15

14

25

36

14

13

14

14

14

50

59

14

14

15

14

14

100

112

14

15

16

15

15

150

183

15

15

15

16

15

257

137

15

16

17

17

16

366

181

15

16

17

18

16

546

255

16

15

17

17

16

Ratios

1 2

40 A 20

n

6546 days 1 2546 " 0546 "

1.1 0.8 1.1

Chart 11 The radial basal breadth of the outer pillar (not pillar cell) table 29, figure 2, distance 7.

their whole length, we can easily measure this distance. After twelve days, however, the breadth consists of the sum of the radial breadth of the outer pillar and the half of the radial distance between the outer corner of the inner pillar and the inner corner of the outer pillar, as previously explained.

In table 28 are given the values for the radial basal breadth of the outer pillar cell (including the outer pillar) from birth to nine days of age. These values show a rapid increase. According to the turn of the cochlea, the breadth at birth diminishes from the base to the apex. At three days it increases already in turn II, but at the later ages it increases gradually from the base to the apex.

TABLE 30 Condensed

Ratios of the radial basal breadth of the outer pillars on age according to the

turns of the cochlea

RATIOS BETWEEN TURNS

AGE

BODY WEIGHT

I-II

I-III

I-IV

days

grams

8

11

1 -1.2

1 1.3

1 1.5

14

13

1.4

1.5

1.3

189

124

1.0

1.1

1.1

In table 29 (chart 11) are given the values for the radial basal breadth of the outer pillar (not pillar cell). As in the case of the inner pillar, here also the outer pillar first appears distinctly at six days of age. After the continuous increase of the values till twelve to fifteen days, they decrease suddenly at twenty days, and then increase again very slowly. This relation is clearly shown by the ratios at the bottom of the last column. That the values tend to increase from the base toward the apex is also shown, though there are some exceptions. Table 30 gives the condensed results.

From Retzius' work ('84) we have calculated the values for the radial basal breadth of the outer pillar in the rabbit and cat as follows (table 31).

There are large differences between my results and those of Retzius during the earlier stage, especially in the rabbit.

60

ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

At birth, the inner pillar has not yet distinctly developed at the base of the pillar cell in the rabbit and the rat, as above stated. We know that the development of the elements of the cochlea proceeds generally from the axis to the periphery, as

TABLE 31

Radial basal breadth of outer pillar measured in n (from Retzius)

RABBIT

CAT

Age

Basal turn

Middle turn

Apical turn

Average

Basal turn

Middle turn

Apical turn

Average

days

,

New-born

15?

12?

7?

11?

25

15

2

50

45

44

46

3

20

7

28

28

17

24

18

20

18

19

10

31

30

37

33

11

30

19

14

28

25

18

24

30

10

15

15

13

TABLE 32

Radial basal breadth of the outer pillar cells on age, based on tables 22, 28, and

29 (charts 12 and 18)

AGE

BODY WEIGHT

TURNS OP THE COCHLEA M

I

II

III

IV

Average

days

grams

1

5

10

9

8

8

9

3

8

15

16

15

12

15

6

11

26

28

28

33

28

9

10

26

30

30

35

30

12

13

33

38

48

52

43

15

13

35

44

50

48

44

20

29

35

40

49

49

43

25

36

35

42

48

48

43

50

59

35

41

49

51

44

100

112

36

45

52

54

47

150

183

36

45

49

54

46

257

137

38

44

50

53

46

366

181

38

43

51

55

47

546

255

40

45

53

54

48

Ratios 1 546 days

9546 " 12546 " 20546 "

1 :5.4

1.6

1.1

1.1

Held ('09) and others have pointed out. Yet, according to Retzius, the outer pillar develops in the rabbit earlier than does the inner pillar. This result seems to me very peculiar, but, at present, I am unable to explain it.

In table 32 (charts 12 and 13) are given the values for the radial basal breadth of the outer pillar cells. These data are derived from tables 22, 28, and 29. At the foot of the last column are given the ratios from 1 to 546, 9 to 546, 12 to 546, and 20 to 546 days. The values increase rapidly during the earlier stage, but after twelve days very slowly, as the ratios show. The breadth is, at birth, largest in the basal and smallest in the apical turn. Very soon, however (six days), the reverse relation appears, and the breadth increases from the base to turn III relatively rapidly, but from turn III to IV slowly. In table 33 the ratios are given in a condensed form. The radial breadth of the outer pillar cells as given by Retzius ('84) are as follows (table 34.)

Chart 13 The radial basal breadth of the outer pillar cell, according to the turns of the cochlea, table 32, figure 2, distance 9.

TABLE 33 Condensed

Ratios of the radial basal breadth of the outer pillar cells on age according to

turns of cochlea

RATIOS BETWEEN TtTRNS

AGB

BODY WEIGHT

I-II

i-in

I-IV

days

grams

1

5

1 :0.9

1 0.8

1 :0.8

8

11

1 1.1

1.2

1.3

18

21

1.2

1.4

1.4

213

138

1.2

1.4

1.4

TABLE 34 Radial basal breadth of the outer pillar cells in n (Retzius)

RABBIT

CAT

AOE

Basal turn

Middle turn

Apical turn

Average turn

Basal turn

Middle turn

Apical turn

Average turn

days

New-born

21

22

23

22

36

30

30

32

3

30

40

30

33

3

36

30

7

65

66

60

64

36

54

36

42

10

52

60

69

60

'

11

50

60

18

43

14

57

80

80

72

30

60

60

This table shows that the breadth of the outer pillar cell increases in the rabbit and the cat continuously from birth to old age, as I have found in the rat. Also the value is generally smallest in the base, largest in the apex, though there are some exceptions. The main differences between the results of Retzius and mine is that the values in the rabbit are larger than in the rat. This is probably due to the differences in the size of the animals.

6. The radial distance between the habenula perforata and the outer border of the foot of the outer pillar cell

The determination of this distance is deemed necessary not only as a datum on growth in general, but also for its bearing on the difficult question of the shifting of the outer pillar cell, to be discussed later. On the other hand, this distance is identical with the radial length of the zona arcuata of the membrana basilaris (table 7. inner zone).

In table 35 (chart 14) are given the values for the radial distance between the habenula perforata and the outer corner of the outer pillar cell at base. At the foot of each column are given the ratios at 1 to 12, 1 to 20, 1 to 546, and 20 to 546 days. As table 35 shows, the distance increases continuously from birth to old age, rapidly up to twelve days, but later gradually. Up to three days the distance is slightly larger in the lower turns, but after this age the relation is reversed, and this persists through life.

The increasing ratio of the distance for each turn according to age is smallest in turn I and largest in turn IV. The ratios for the condensed data are given in table 36. While the ratio at birth is the same in each turn, 1:1.0, that of turn I to II is smallest for every condensed age. Also it is to be seen that the increase of the ratio in turn I to II is smallest and that in turns I to IV is largest. In Retzius' work ('84) we find the following values for this distance (table 37).

Table 37 shows that in the rabbit the growth changes are similar to those in the rat, though the absolute values are somewhat larger. As hi preceding determinations, the values for the cat do not stand in the same relation as those for the rabbit, but indicate precocity. Some corresponding observations by Hensen, Bottcher, and others will be presented later.

7. The greatest height of the greater epithelial ridge (der grosse Epithelwulst (Bottcher) s. Organon Kollikeri) resp. of the inner supporting cells

(fig. 4, G). The so-called greater epithelial ridge is a prominence formed by high cylindrical pseudostratified cells. It is situated axialward on the tympanic wall and continued outward to the lesser epithelial ridge. About the fate of this ridge there were various divergent opinions among the older authors. Now, the view of Bottcher ( '69) is generally accepted. This large prominence vanishes during development, and instead of it a deep and wide furrow lined with low epithelium appears. These epithelial cells become peripherally higher and finally lean

Online Editor - TABLE 35 (to be formatted)

TABLE 35 Radial distance between habenula perforata and the outer corner of the outer pillar cells at base on age (chart 14)- For the average values see the third column in table 9 AGE BODY WEIGHT TURNS OF TBE COCHLEA M I II III IV Average days yrams 1 5 50 50 48 48 49 3 8 63 65 64 58 63 6 11 64 73 86 86 77 9 10 70 76 86 86 80 12 13 69 83 98 100 88 15 13 70 84 98 95 87 20 29 71 81 96 98 87 25 36 71 86 95 97 87 50 59 69 83 96 102 88 100 112 73 88 101 106 92 150 183 73 89 98 107 92 257 137 76 87 98 107 92 366 181 76 89 100 107 93 546 255 78 89 104 106 94 Ratios 1 12 days 1 20 " 1546 " 20546 " 1.4 1.4 1.6 1.1 1.7 1.6 1.8 1.1 1 -2.0 2.0 2.2 1 :2.1 2.0 2.2 1.1 1.8 1.8 1.9 1.1 100 80 60 40

Chart 14 The radial distance between the habenula perforata and the outer corner of the outer pillar cell at base, table 35, figure 2, distance 5.

on the inner supporting cells, which are termed ' Grenzzellen ' by Held ('02). The latter belong, of course, to this ridge, since the inner hair cell marks the outmost row in the ridge. The 'Grenzzellen' of Held, however, are different from other high cylindrical cells in the ridge, as they have a very intimate relation with the ' Phalangenzellen ' of Held, stand with their bases just

TABLE 36 Condensed

Ratios of the radial distance between the habentda perforata and the outer corner of the outer pillar cells at base on age

RATIOS BETWEEN TURNS

AVERAGE AGE

AVERAGE BODY

WEIGHT

I-II

i-in

I-IV

days

grams

1

5

1 :1.0

1 :1.0

1 :1.0

8

11

1.1

1.3

1.2

18

21

1.2

1.4

1.4

213

138

1.2

1.3

1.4

TABLE 37

Radial distance between habenula perforata and the outer corner of the outer pillar cells at base in n (Retzius)

RABBIT

CAT

Age

Basal

Middle

Apical

Average

Basal

Middle

Apical

Average

turn

turn

turn

turn

turn

turn

turn

turn

days

New-born

75

80

75

77

105

105

120

110

2

80

90

100

90

3

80

120

7

100

115

107

107

78

110

120

103

10

100

120

129

116

11

120

129

108

119

14

106

140

129

125

30

85

120

120

108

outward from the habenula perforata and serve to support the inner hair cell as Deiters' cells support the outer hair cells.

Thus the greater ridge includes in its prominence three kinds of cells, the high cylindrical cells, the 'Grenzzellen' of Held and the inner hair cell.

The greatest height of this ridge is not situated at a fixed point, but first lies somewhat outward from the middle part and

66

ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

after the furrow appears, passes outward towards the inner supporting cells. Thus the greater ridge decreases in thickness from birth to nine days of age, then increases gradually to twenty days. After twenty-five days the values diminish again very slowly but continuously.

In table 38 (charts 15 and 16) are given the values of the greatest height of the greater epithelial ridge from the basilar membrane

TABLE 38

Greatest height of the greater epithelial ridge (resp. of the inner supporting cells)

on age (charts 15 and 16)

Bodv wcifitlitj

TURNS OF COCHLEA M

I

II

III

IV

Average height

days 1

grams 5

68

65

66

63

66

3

8

49

49

56

57

53

6

11

40

40

41

40

40

9

10

36

40

41

42

40

12

13

38

41

48

53

45

15

13

44

46

52

58

50

20

29

50

53

63

66

58

25

36

51

51

63

63

57

50

59

50

50

59

63

56

100

112

48

49

59

63

55

150

183

47

49

56

61

53

257

137

47

51

56

62

54

366

181

46

49

57

60

54

546

255

44

50

56

60

53

Ratios 1 9 days 1:0.6

12 20 " :1.3

12546 " :1.2

20546 " :0.9

1546 " :0.8

through the summit of the supporting cells, according to age. At the bottom of the last column is given the ratio at 1 to 9, 1 to 546, 12 to 20, 12 to 546, and 20 to 546 days of age.

The values in turn I are at birth the largest, but at three days the relation is reversed and remains so in the later age groups. Table 39 shows this relation from the condensed data.

Retzius ('84) gives in the rabbit and cat the following values (table 40).

In the rabbit the values decrease from birth till ten days, then increase; therefore, they agree in general with my results

50 40 30

25

50 50 10O 20O 30O 40O 500

Chart 15 The greatest height of the greater epithelial ridge (resp. of the inner supporting cells) table 38, figures 4 to 12.

70 44

60

5O 40 30

s

o

25

50

50 IOO 20O 3OO 4OO 500

Chart 16 The greatest height of the greater epithelial ridge (resp. of the inner supporting cells) arranged according to the turns of the cochlea, table 38, figures 4 to 12.

on the rat, while in the cat they diminish from birth till thirty days though irregularly.

The absolute values are greater for the rabbit than for the rat during the earlier stage, but afterwards they are similar.

68

In the cat the early data give values similar to those for the rat, but the later values are lower.

Bottcher's observations ('69) on the cat, calf, and sheep also give larger values than mine. In the cat the greater ridge has an average height of 75 [x and in both the others of 90 \L. Therefore, even in the same animal (cat) there are large differences in the data presented by different authors.

TABLE 39 Condensed

Ratois of the greatest height of the greater epithelial ridge (resp. of the inner supporting cells) according to the turns of the cochlea on age

Average age

Average body weight

RATIOS BETWEEB TURNS

I-II

i-in

I-IV

days

grams

1

5

1 :1.0

1 1.0

1 :0.9

8

11

1.0

1.1

1.2

18

21

1.1

1.2

1.3

213

138

1.0

1.2

1.3

TABLE 40

Greatest height of the greater epithelial ridge measured through the inner supporting

cells, in p. (Retzius)

RABBIT

CAT

Age

days

Basal turn

Middle turn

Apical turn

Average turn

Basal turn

Middle turn

Apical turn

Average turn

New-born

78

99

90

89

45

75

6S

63

2

60

90

90

80

3

40

84

7

51

68

63

61

40

54

63

52

10

36

54

56

49

11

50

58

66

58

14

51

51

51

51

30

30

.

45

45

40

Gottstein ('72) thinks that the greater epithelial ridge does not diminish its height for some time after birth, but through the outward development of the labium tympanicum, and in addition to this through the growth of the labium vestibulare, the sulcus spiralis internus arises. He does not give measurements.

His idea was strongly opposed by Bottcher ( 72) and my results are also opposed to Gottstein's view.

8. The radial distance between the labium vestibulare and the habenula perforata

The purpose of this measurement is to determine how the habenula perforata stands in relation to its surroundings during the development of the cochlea. The measurements of this distance is difficult. During the earlier stages, the labium vestibulare is quite undeveloped, especially in the upper turns. At birth we see on the inner surface of the greater epithelial ridge a small prominence under which the epithelial cells are short and pressed together so that the nuclei seem to be arranged in several rows (fig. 4). This appearance is due to the invasion of the subjacent connective tissue into the epithelium.

Thus the vestibular lip arises. We do not see a furrow at this time and cannot use the top of the furrow as a point for measuring as did Hensen ('63) in the ox and Bottcher ('69); in the embryo cat). To the measure the distance between the insertion of Reissner's membrane and the habenula perforata has no meaning for my purpose, because the length of the limbus laminae spiralis changes with age.

Thus I have measured the distance between the small epithelial prominence on the axial side of the greater ridge, corresponding to the edge of the labium vestibulare, and the habenula perforata.

In table 41 (charts 17 and 18) are given the -values of the radial distance between the labium vestibulare and the habenula perforata. At the foot of the last column are given the ratios from 1 to 546, 9 to 546, and 20 to 546 days. As we see, the values are a little bit smaller at the earlier stage. After nine days they are almost the same in every stage. The small differences at the earlier and later stages are probably due to the retarded development of the labium vestibulare.

When we consider the values for this distance in each turn, it is evident that these increase from base to apex. In the condensed table 42 this relation is shown.

Hensen ('63) finds that the distance from the top of the furrow to the habenula perforata is in the fetal calf and in the ox the. same, 255 [x. He considers the holes of the habenula as a ' punctum fixum. ' Bottcher ('69, 72) agrees with Hensen and gets in the cat embryo and the adult cat the following values (table 43).

TABLE 41

Radial distance between the labium veslibulare and the habenula perforata on age

(charts 17 and 18)

AGE

BODY WEIGHT

TURNS OP THE COCHLEA M

I

II

III

IV

Average

days

grams

1

5

100

108

120

130

115

3

8

80

110

130

137

114

6

11

82

105

135

137

115

9

10

83

108

137

145

118

12

13

80

102

139

148

117

15

13

82

107

144

157

122

20

29

84

106

146

153

122

25

36

82

105

147

150

121

50

59

82

104

137

147

118

100

112

80

103

151

154

122

150

183

80

107

141

144

118

257

137

83

105

143

150

120

366

181

79

105

135

149

117

546

255

79

105

143

150

119

Ratios 1 546 days

9546 " 20546 "

1.0 1.0 1.0

TABLE 42 Condensed

Ratios of the radial distance between the labium vestibulare and the habenula perforata according to turns of the cochlea

RATIOS BETWEEN TURNS

AVEKAGE AGE

WEIGHT

I-II

I-II I

I-IV

days

grams

1

5

1 1.1

1 1.2

1 1.3

5

10

1.3

1.6

1.8

141

93

1.3

1.7

1.8

Comparing the results of both Hensen and Bottcher with my own, the values obtained by Hensen are large, as would be expected in the larger animal. The cat and rat however, give similar values. We conclude, therefore, that broadly speaking, the habenula perforata is to be considered as a 'punctum fixurn, 'at least after birth.

9. The radial distance between the labium vestibulare and the inner edge of the head of the inner pillar cell

To measure the

140

120

1OO

AGE DAYS

25

50

50 1OO 2OO 3OO 40O 500

Chart 17 The radial distance between labium vestibulare and the habenula perforata, table 41, figure 10.

Chart 18 The radial distance between labium vestibulare and the habenula perforata according to the turns of the cochlea, table 41.

radial breadth from the labium vestibulare to the inner edge of the head of the inner pillar cell, I have used, at earlier stages, as in the preceding chapter, the same small prominence as an inner fixed point (fig. 4). In table 44 (chart 19) are given the values for this radial distance according to age. At the bottom of the last column are given the ratios from 1 to 9, 1 to 546

TABLE 43

Distance between labium vestibulare and habenula perforata in n (Bottcher)

PLACE OF

CAT EMBRYO 9 CM.

CAT EMBRYO 11 .5

CAT THREE DAYS

ADULT CAT

MEASUREMENT

LONG

CM. LONG

OLD

I turn

120

120

120

100

II turn

130

130

130

110

III turn

150

140

140

130

TABLE 44

Radial distance between the labium veslibulare and the inner edge of the head of the inner pillar cell on age (chart 19)

AGE

BODY WEIGHT

TURNS OF THE COCHLEA M

I

II

ill

IV

Average

days

grams

1

5

111

126

138

130

126

3

8

84

118

150

170

131

6

11

88

119

159

180

136

9

10

94

131

168

179

143

12

13

69

97

138

156

115

15

13!

",' 66

103

137

149

114

20

29

66

103

137

148

114

25

36

65

100

136

148

112

50

59

61

98

129

144

108

100

112

64

99

139

153

114

150

183

60

99

129

143

108

257

137

67

100

134

149

113

366

181

60

102

130

151

111

546

255

55 :..

99

128

143

106

Ratios 1 9 days

1546 " 12546 "

1.1

0.8 0.9

TABLE 45 Condensed

Ratios of the radial distance between the habenula perforata and the inner edge of

the head of the inner pillar cell according to the turns of

the cochlea on age

KATIOS BETWEEN TURNS

AVERAGE AGE

WEIGHT

I-II

I-HI

I-IV

days

grams

1

5

1 1.1

1 \.9

1 1.2

6

10

1.4

1.8

2.0

154

102

1.5

2.1

2.3

and 12 to 546 days of age. As the table shows, the values increase in general from birth to nine days; therefore, the surface of the greater epithelial thickening from the labium vestibulare to its outer boundary becomes, during the earlier stage, wider and wider, then decreases sharply, and after that continuously but slowly. This sudden diminishing of the distance has a very intimate relation with the change in the form of the papilla spiralis at this stage of development.

This point I will discuss later.

That the values increase from the base to the apex first rapidly and later less rapidly, is also to be seen here. Table 45 shows this relation clearly. It is remarkable, however, that the ratio becomes

Chart 19 The radial distance between the labium vestibulare and the inner edge of the head of the inner pillar cell, table 44.

at each turn larger with age, although the absolute value is after nine days generally smaller than at the preceding age. Therefore, we see that the diminution of the distance after nine days is largest in the basal turn and smallest in the apical. Hensen ('63) asserts that there is a movement axialward of the organ of Corti (resp. the head of the pillar cell), but gives no measurements. Neither Bottcher nor Retzius measured this distance. Prentiss ('13, page 445) states that "the distance between the inner angle of the cochlea and the pillar cells, two definite points, may be measured with considerable accuracy and shows no important change in the position of the spiral organ from the 13 cm. to the 18.5 cm. stage, nor later in the new born animal" (pig) But he also does not record his measurements.

Hardesty ('15, p. 54) says "that the space occupied by the width of the greater epithelial ridge increases throughout the coils of the cochlea up to pigs of 15 to 16 cm., and thereafter it begins to decrease very perceptibly." He measured the width from the membrana propria of the epithelium of the greater ridge, at its most axial extension under Huschke's teeth, to the apical end of the inner hair cell of the spiral organ. " The

TABLE 46

Vertical distance from the membrana basilaris to the surface of the pillar cells on

age (chart 20}

TURNS OF THE COCHLEA M

AGE

BODY WEIGHT

I

II

ill

IV

Average

days

grams

1

5

35

36

39

36

37

3

8

30

29

29

29

29

6

11

29

32

31

29

30

9

10

32

33

35

36

34

12

13

41

45

50

52

47

15

13

44

48

53

57

51

20

29

53

57

67

71

62

25

36

55

56

66

68

61

50

59

53

55

67

68

61

100

112

53

54

64

67

60

150

183

52

54

63

66

59

257

137

53

56

63

69

60

366

181

51

56

66

67

60

546

255

52

55

62

66

59

Ratios 1 12 days 1-1.3

1 20 " 1.7

1546 " 1.6

12546 " 13

20546 " 1.0

method of measurement differs from mine, so the results cannot be compared directly. While the distance in the rat increases to nine days of age, that in the pig decreases perceptibly in fetuses more than 16 cm. long.

According to Hardesty ('15, p. 55). "the decrease in the I and III half turns may be as much as one-third of the width of the greater ridge when at its maximum size and activity. " And "after the tectorial membrane is about completely produced,

GROWTH OF THE INNER EAR OF ALBINO RAT

75

and while the spiral organ is enlarging, the inner hair cells, and therefore the organ, may be moved in the apical coil of the cochlea axialward a distance of about half the maximum width of the greater epithelial ridge, "

The differences of the values in the rat at 9 and 546 days are in the basal and apical turn about the same, 39 and 36 n, respectively (table 44). Thus while the inner edge of the inner pillar cell approaches at 546 days in the basal turn by as much as 41 per cent of the distance present at nine days, that in the apex moves only 20 per cent inward in old age. This result is the reverse of that obtained in the pig by Hardesty. The reason for this contradiction I will discuss later.

Chart 20 The vertical distance from the membrana basilaris to the surface of the pillar cells, table 46, figure 1, 1-1.

10. The vertical distance from the membrane basilaris to the summit of the pillar cells

The method of getting the vertical distance from the membrana basilaris to the surface of the pillar cells is shown in figure 1, line 1-1. In table 46 (chart 20) are given the values thus obtained. At the foot of the last column are given the ratios of this distance at 1 to 12, 1 to 20, 1 to 546, 12 to 546, and 20 to 546 days. The average value is relatively large at birth, it diminishes at three days, then increases more rapidly to twenty days. After this it decreases very slowly. The maximum height of the arch of Corti is at twenty days of age. Comparing the values for the height in each turn, we find that from nine days they increase from the basal to the apical turn. This relation can be easily seen in table 47.

Retzius ( '84) gives in the rabbit and cat the following values (table 48).

TABLE 47 Condensed

Ratios of the vertical distance from the membrana basilaris to the surface of the pillar cells according to the turns of the cochlea

RATIOS BETWEEN TURNS

AVERAGE BODY

AVERAGE AGE

WEIGHT

I-II

i-ni

I-IV

days

grams

1

5

1 :1.0

1 : 1.1

1 : 1.0

1

11

1.1

1.1

1.1

18

21

1.1

1.2

1.3

213

138

1.0

1.2

1.3

TABLE 48 Vertical distance from the membrana basilaris to the summit of the pillar cells

BABBIT

CAT

Age

Basal

turn

Middle turn

Apical turn

Average

Basal turn

Middle turn

Apical turn

Average

days

New-born

45

70

61

59

45

60

48

51

2

45

69

40

51

3

39

60

7

46

60

60

55

45

47

50

44

10

45

69

69

61

11

JK

50

60

42

51

14

45

57

66

56

30

' }'

33

51

57

47

Table 48 shows that the height of the arch of Corti in the rabbit approximates that in the rat, though there are considerable differences in the earlier stages. In the former the arch of Corti develops after: birth only a little, and is therefore more precocious than in the rat. In the cat the same relation is to be seen, but the absolute values in the latter animal are smaller than in either the rabbit or the rat.

11. The greatest height of the tunnel of Corti

Some authors have reported in several animals the appearance of the tunnel of Corti just after birth, or even in later intrauterine life. In the rat, however, it first appears through all the turns after the ninth day. Sometimes we see it at nine days in the lower turn, though not yet in the upper. The method of measuring the height is shown in figure 1, line 1-1'. Table 49 (charts 21 and 22) gives the values for the greatest height of the tunnel of Corti. At the foot of the last column are given the ratios from 12 to 25, 12 to 546, and 25 to 546 days.

As the table shows, the space appears in all the turns at twelve days and has considerable height. This increases to twenty-five days, than decreases very slowly. This increase and decrease correspond to the changes in the distance of the summit of the pillar cells from the basilar membrane.

When we consider the height in each coil of the cochlea, we find the value increases from the base to the apex, first rapidly then slowly. In table 50 this relation is clearly shown.

Retzius ('84) gives the values for the adult rabbit, man and cat (one month) as follows (table 51).

According to this table, the average height is in the adult man, cat, and rabbit somewhat less than in the rat.

12. The height of the papilla spiralis at the third series of the outer hair cells

The measurements were taken along the line 2-2 shown in figure 1. The growth of this vertical height depends not only upon the increase of the length of the corresponding outer hair cell, but chiefly upon the development of the Deiters' cells, especially of the outermost row, and of the sustentacular cells of Hensen.

In table 52 (charts 23 and 24) are given the values for this vertical height of the papilla spiralis at the third series of the outer hair cells according to age. At the bottom of the last column are the ratios at 1 to 12, 1 to 20, 1 to 546, and 20 to 546 days. The heights decrease at three days, but increase from nine to twelve days very rapidly, nearly doubling their minimal values, and reach a maximum at twenty days. After that time they decrease very gradually to the end of the record. Therefore, the difference between the ratios at 1 to 20 and 1 to 546 days is very small.

Online Editor - TABLE 49 (to be formatted)

TABLE 49 Greatest height of the tunnel of Corti on age (charts 21 and 22} AGE BODY WEIGHT TURNS OP THE COCHLEA M I II ill IV Average days grams 1 5 3 8 6 11 9 1 10 12 13 29 33 39 37 35 15 13 31 34 42 46 38 20 29 37 42 52 56 47 25 36 39 41 54 56 48 50 59 38 41 53 57 47 100 112 38 43 51 56 47 150 183 37 41 49 54 45 257 137 38 43 51 56 47 366 181 37 41 52 53 46 546 255 36 39 48 53 44 Ratios 12 25 days 12546 " 25546 " 1.4 1.3 0.9 1 In one case nine days old which could hear the space was found through all the turns of the cochlea.

Online Editor - TABLE 50 (to be formatted)
TABLE 50 Condensed Ratios of the greatest height of the tunnel of Corti according to the turns of the cochlea on age , RATIOS BETWEEN TURNS AVERAGE BOOT AVERAGE AGE WEIGHT I-II i-ni I-IV days grams 12 13 1 : 1.1 1 1.3 1 1.3 18 21 1.1 1.4 1.5 213 138 1.1 1.3 1.4

Online Editor - TABLE 51 (to be formatted)
TABLE 51 The greatest height of the tunnel of Corti in n (Retzius) RABBIT CAT (one month) MAN Basal Middle Apical Average Basal Middle Apical Average Basal Middle Apical Average 30 39 36 35 18 37 36 30 28 45 49 41

At twelve days and after, the values for the height increase in passing from the base to the apex, at first rapidly, then more slowly. In the earlier stages this relation is obscure or reversed.

Chart 21 The greatest height of the tunnel of Corti, table 49, figure 1, 1-1

Chart 22 The greatest height of the tunnel of Corti, according to the turns of the cochlea, table 49.

In the condensed table 53 are given the ratios in each turn. While the ratio of each turn before eight days is about 1:1.1, and between turns I and II remains constant in the later age, that for I to III and I to IV is at 18 and 213 days decidedly larger. Therefore, the increase of the height is most marked in the III and IV turn, as shown in chart 24.

Online Editor - TABLE 52 (to be formatted)

TABLE 52 Height of the papilla spiralis at the third series of outer hair cells on age (charts 23 and 24) AGE BODY WEIGHT TURNS OF THE COCHLEA M I II III IV Average days grams 1 5 35 35 39 28 34 3 8 22 23 25 26 24 6 11 25 24 25 23 24 9 10 28 28 27 28 28 12 13 40 49 54 56 50 15 13 46 53 65 66 58 20 29 56 61 76 81 69 25 36 56 61 76 78 68 50 59 53 59 78 80 68 100 112 54 59 74 79 67 150 183 55 57 75 77 66 257 137 54 59 74 81 67 366 181 5? 58 75 78 66 546 255 52 58 72 75 64 Ratios 1 12 days 1 1.5 1 20 " 2.0 1546 " 1.9 20546 " 0.9

Online Editor - TABLE 53 (to be formatted)
TABLE 53 Condensed Ratios of the height of the papilla spiralis at the third series of outer hair cells according to the turns of the cochlea on age AVERAGE AGE AVERAGE BODY WEIGHT BATIOS BETWEEN TURNS I-II i-ni I-IV days grams 1 5 1 :1.0 1 :1.1 1 0.8 8 11 1.1 1.1 1.1 18 21 1.1 1.4 1.5 213 138 1.1 1.4 1.5

TABLE 54 Height of the papilla spiralis at the third scries of outer hair cells in n (Retzius)

BABBIT

CAT

AGE

Basal turn

Middle turn

Apical turn

Average

Basal turn

Middle turn

Apical turn

Average

days

New-born

48

70

60

59

45

60

45

50

2

45

70

54

56

3

40

58

7

54

69

66

63

42

5<

48

49

10

42

86

84

71

11

60

72

42

58

14

60

87

90

79

30

36

57

70

54

80

GROWTH OF THE INNER EAR OF ALBINO RAT

81

Retzius ('84) finds in the rabbit and cat the [values for this height given in (table 54).

Comparing these average numbers with mine, it appears that the height in the rabbit is greater, and in the cat smaller than

u

70 5O 30 10

k

AGE

o

25 5O 50 |OO 2OO 3OO 40O 5OO

Chart 23 The height of the papilla spiralis at the third series of the outer hair cells, table 52, figure 1, 2-2.

90

70

50

30

10

AGE DA.YS

O

25

50

5O 1OO 2OO 3OO 4OO 5OO

Chart 24 The height of the papilla spiralis at the third series of the outer hair cells, according to the turns of the cochlea, table 52.

in the rat. In both animals the values increase rapidly at ten to eleven days of age, as in the albino rat, but the height in these animals is at the earlier stage almost twice as large as in the rat. Hardesty ('15) measured the thickness of the organ of Corti in

82

ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

the pig in a somewhat different way, using the vertical line from the basilar membrane proper through the m'ddle of the outer hair cell to the surface of the organ, and found the increase in thickness to take place most rapidly at the stages before full term, though it seems to continue after birth. I have not made cor TABLE 55

Greatest height of Hensen's supporting cells on age (chart 25)

AGE

BODY WEIGHT

TURNS OP THE COCHLEA M

1

II

III

IV

Average

days

grams

I

5

36

36

38

31

35

3

8

18

21

21

24

21

6

11

21

20

21

18

20

9

10

20

23

23

24

23

12

13

40

49

56

58

51

15

13

44

56

69

72

60

20

29

64

64

86

87

75

25

36

69

71

84

86

78

50

59

71

74

87

89

81

100

112

77

. 78

87

89

83

150

183

76

77

<3

93

85

257

137

81

83

89

89

86

366

181

82

83

89

91

86

546

255

79

79

92

93

86

Ratios 1 6 days

1 12

1 20

1546

6 12

6 20

6546 12 20 12546 20546

0.6 1.5 2.1 2.5 2.6 3.8 4.3 1.5 1.7 1.1

responding studies on the rat. In the latter animal, however, the rapid increase usually appears at twelve days of age, when the animal as a rule first responds to auditory stimuli, and thus we have a correlation between the development of the organ and the beginning of the function, which will be discussed later. In the case of one rat that could hear at nine days this change had already occurred.

13. The greatest height of Hensen's supporting cells

The older authors (Kolliker and others) thought that the arch of Corti marks the highest point of the papilla which slopes from this point gradually outward to the cells of the zona pectinata. Against this erroneous idea Hensen ('63) first published observations showing that the highest point is in the papilla which ascends laterally from the outer hair cells, and then slopes abruptly and passes over to the cells of the sulcus spiralis externus. We term this prominence Hensen's prominence and the cells, Hensen's supporting cells. The measurements of the height of these cells were made along 3 3 in figure 1. Table 55 (chart 25) shows the values for the greatest vertical height of these supporting cells according to age. At the foot of the last column are given the ratios from 1 to 6, 1 to 12, 1 to 20, 1 to 546, 6 to 12, 6 to 20, 6 to 546, 12 to 20, 12 to 546, and 20 to 546 days. The values diminish at the earlier stage from birth to six or nine days. At twelve days they increase suddenly, more than doubling. After that they increase to old age, rapidly up to twenty days and then slowly. Here also the height increases from the base to the apex, the most marked increase occurring between turns II and III. In table 56 this relation is clearly shown. Retzius ('84) gets values of this height in the rabbit and cat as follows (table 57).

Chart 25 The greatest height of Hensen's supporting cells, table 55.

In both the rabbit and the cat the height increases at ten to eleven days very considerably, as it does in the rat. Only there is a large difference in the absolute values for the three animals, these being largest in the rabbit and smallest in the cat. The final average values in the cat are nearly the same as those in the rat at the same age.

Kolmer ('07) finds in the calf the value in the highest point of the organ of Corti in the region of the innermost Hensen's cells as follows:

In the basal turn, 84 [A

In the second turn, 90 JJL

In the third turn, 105 [JL

Average, 93 [i.

Hensen ('63) gives in man the average height of the papilla as 90 (JL in the hamulus and 60 [j. in the radix. Thus the height of Hensen's cells is different in different animals.

When we consider the growth in the height of Hensen's cells we can picture the change of the form in the papilla spiralis. As shown already, the height of the pillar cells is largest at the earlier stage, when the papilla has its highest point at the summit of the arch of Corti, and slopes downward to the Hensen's cells. But at twelve days the form is reversed, and the highest point is in Hensen's prominence from which the surface slopes inward more or less steeply to the surface of the pillar cells and the inner supporting cells. Thus the surface of the papilla does not run parallel to the basilar membrane, but makes with it a sharp angle opening outward. This angle has been measured.

14. The angle subtended by the extension of the surface of the lamina relicularis with the extended plane of the membrana basilaris

As just stated, the lamina reticularis after the earlier stages is not parallel to the membrana basilaris, but forms an angle with it. The measurements of this angle , were taken as shown in lines 4~4' i n figure 1. In table 58 (chart 26) are given the values for the angle in degrees. Before nine days there is no appreciable angle. From twelve to twenty days the angle increases rather rapidly, and after twenty days continuously but slowly. The ratio at the bottom of the last column shows this clearly.

Comparing the values of the angle in each turn according to age, there is no clear evidence that it increases from base to apex, though it tends to be largest in turn III and next largest in turn II. The condensed table 59 shows these relations. Retzius ( ; 84) finds this angle in the rabbit and cat to be as in table 60.

TABLE 56 Condensed

Ratios of the greatest height of Hensen's supporting cells according to the turns of the cochlea

RATIOS BETWEEN SUCCESSIVE TURNS

AVERAGE AGE

AVERAGE BODY

WEIGHT

1

I-II

I-III

I-IV

days

grams

1

5

1 1.0

1 1.1

1 0.9

8

11

1.1

1.2

1.2

18

21

1.1

1.4

1.5

213

138

1.0

1.2

1.2

TABLE 57 Greatest height of Hensen's supporting cells in M (Retzius)

RABBIT

CAT

Age Days

Basal turn

Middle

Apical

Average

Basal

Middle

Apical

Average

Xew-born

38?

60?

50?

49?

45

50

39

45

2

55?

60?

3

39

54

7

48

81

67

65

57

50

40

49

10

105

125

105

112

11

75

78

45

66

14

150

120

30

50

69

95

71

Retzius also finds in man in the basal turn 25, in the middle 35, and in the apical 23. Thus the angle always increases with age, but has different absolute values in different mammals and always tends to be greater in the middle turns.

15. Lengths of the inner and outer pillar cells. The measurements of length were taken as shown by lines 1-1, and 2-2 as in figure 2. This does not give the total length, but the length from the base to the point, just below the joint. As is well

TABLE 58

Angle of the lamina reticularis with the plane of Ihe membrana basilaris in

degrees, 6 (chart 26}

TURNS OF THE COCHLEA DEGREES

AGE

BODY WEIGHT

I

II

III

IV

Average

days

grams

1

5

3

8

6

11

9

10

12

13

7

12

13

9

10

15

13

11

14

13

13

13

20

29

15

13

11

11

13

25

36

14

14

13

13

14

50

59

15

15

17

11

15

100

112

15

14

16

14

15

150

183

15

15

19

17

17

257

137

13

15

18

17

16

366

181

16

15

16

16

16

546

255

16

16

17

17

17

Vertical averages

13.7

14.3

15.3

13.8

Ratios 12 20 days 1 : 1.3

12546 " :1.7

TABLE 59 Condensed

Ratios of the angle of the lamina reticularis with the plane of the membrana basilaris according to the turns of the cochlea

RATIOS BETWEEN TURNS

AVERAGE AGE

AVERVGE BODY WEIGHT

I-II

I-II I

I- IV

days 12

grams 13

1 1.7

1 1.9

1 : 1.3

18

21

1.0

0.9

0.9

213

138

1.0

1.2

1.0

TABLE 60

Angle of the lamina reticutaris with the plane of the membrana basilaris in degrees

(Retzius)

Age

Basal turn

Middle turn

Apical turn

Average

Basal turn

Middle turn

Apical turn

Average

days

New-born

5?

8?

5? 8?

2

3

5? 8?

7

17

19

11

5

5

10

10

20

30

23

24

11

20

1020

14

25

50

45

40

30

18

23

20

20

GROWTH OF THE INNER EAR OF ALBINO RAT

87

known, the inner and outer pillar cells when mature show a more or less S-shaped curvature, though they are straighter in the earlier stages. Thus the length as measured in the adult cochlea is somewhat smaller than the natural lengths.

DEGREES 18

15

12

25

50

5O 1OO 20O 300 40O 500

Chart 26 The angle subtended by the extension of the lamina relicularis with the extended plane of the membrana basilaris, in degrees, table 58, fieure 1 4-4', 9 In table 61 (charts 27 to 32) is given the values for the lengths of the inner and outer pillar cells according to age. At first we shall consider the average values for the length of the inner and outer pillar cells taken together. This length diminishes at three days. From three to twelve days it increases rapidly,

88

ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

and from twelve to twenty days more slowly. After twenty days it decreases a little. The ratios at the bottom of the last column show these relations. The familiar fact, that the length increases from the base to the apex is clearly shown in chart 28.

TABLE 61

Lengths of the inner and outer pillar cells (without head) measured from the footplate on the membrana basilaris to the point directly below the junction (charts 27 to 32)

AOE

BODY WEIGHT

INNER PILLAR

OUTER PILLAR

Combined Average

Turns of the cochlea M

Turns of the cochlea M

I

II

ill

IV

Average

I

II ill

IV

Average

days

gms

1

5

28

29

29

29

29

24

27

27

26

26

28

3

8

26

23

26

23

25

19

20

20

21

20

23

6

11

35

36

36

37

36

21

26

27

26

25

31

9

10

35

39

41

40

39

26

26

29

29

28

34

12

13

33

38

44

44

40

46

59

72

72

62

51

15

13

34

38

48

51

43

44

59

74

78

64

54

20

29

43

47

56

60

52

56

65

79

83

71

62

25

36

43

47

56

60

52

53

64

80

84

70

61

50

59

42

44

55

61

51

52

64

79

84

70

• 61

100

112

42

44

53

58

49

52

62

79

84

69

59

150

183

41

43

54

59

49

51

64

76

85

69

59

257

137

40

44

53

60

49

53

64

75

85

69

59

366

181

39

45

53

59

48

50

64

78

83

69

59

546

255

41

44

53

58

49

49

64

78

83

69

59

Ratios 1- 12 days

1 1.4

1 :2.4

1 : 1.8

1- 20 "

1.8

2.7

2.2

1-546 "

1.7

2.7

2.1

20-546 "

0.9

1.0

1.0

When we calculate the average values of the inner and outer pillar cells from Retzius table ('84), we get the following (table 62).

TABLE 62

Combined lengths of the inner and outer pillars from the foot plate to a point directly below the junction in n (Retzius)

RABBIT (adult)

CAT (adult)

MAN (adult)

Basal turn

Middle turn

Apical turn

Average turn

Basal turn

Middle turn

Apical turn

Average

Basal turn

Middle turn

Apical turn

Average

66

85

78

76

55

75

73

67

55

84

87

75

Chart 27 The length of inner and outer pillar cells combined, without head, measured from the foot plate on the membrana basilaris to the point directly below the junction, table 61, figure 2, /-/, 2-2.

Chart 28 The length of inner and outer pillar cells combined, without head, measured from the foot plate on the membrana basilaris to the point directly below the junction, according to the turns of the cochlea, table 61.

Chart 29 The length of inner pillar cell without head, table 61, figure 2, 1-1.

As table 62 shows, the values in these mammals are larger than those in the albino rat a result which fits with our previous observations.

When we consider the length of the inner pillar cells alone, we see that the values (chart 29) here also increases from three days to twenty days, but not so largely as in the combined values of the inner and outer pillar cells. After twenty days the values for the inner pillar cells decrease slightly. This relation is shown by the ratios at the bottom of the corresponding column. That the increase progresses from the base to the apex, being most marked in turn III, is illustrated in chart 30. The condensed table 63 shows those relations also. The one-day-old rat is an exception.

We turn now to the growth in the length of the outer pillar cells. As we see in table 61 (chart 31), the length of the outer pillar cell does not increase so much from one to nine days as the inner pillar cell did. At twelve days, however, the increase in length is very marked, that is, 2.2 times as much as at nine days.

After the outer pillar cell reaches its maximum at twenty days, it decreases only slightly with advancing age. The ratios at the bottom of the corresponding column show this relation clearly. The length increases from base to apex, though this relation is not well established until twelve days, as shown in table 61 and chart 32. The ratios of the outer pillar cells according to the turns of the cochlea are shown in table 64.

The inner and outer pillar cells show marked differences in their growth. While at the earlier ages the length of the inner is greater than that of the outer, yet after twelve days this relation is reversed. Moreover, from nine to twelve days the growth is gradual in the inner pillar cells, but rapid in the outer. The condensed table 65 shows the values for the length of the inner and outer pillar cells separately. In the last column are given the ratios between them.

In the accompanying table 66 I have compared the values obtained in the rat with those given by other authors.

As table 66 shows, the absolute values differ in various animals. However, the ratios between the values for the inner and outer

Chart 30 The length of the inner pillar cell without head, according to the turns of the cochlea, table 61.

Chart 31 The length of outer pillar cells without head, table 61, figure 2,

Chart 32 The length of outer pillar cells without head, according to the turns of the cochlea, table 61.

TABLE 63 Condensed Ratios of the length of the inner pillar cells according to the turns of the cochlea

AVERAGE AGE

AVERAGE BOOT WEIGHT

RATIOS BETWEEN TURNS

I-II

I-II I

I-IV

days 1

grams 5

1 1.0

1 1.0

1 1.0

8

11

1.1

1.2

1.1

18

21

1.1

1.3

1.4

213

138

1.1

1.3

1.4

TABLE 64 Condensed Ratios of the length of the outer pillar cells according to the turns of the cochlea

AVERAGE AGE

AVERAGE BODY WEIGHT

RATIOS

BETWEEN TURNS

I-II

I-II I

I- IV

days 1

grams 5

1 : 1.1

1 1.1

1 1.0

8

11

1.2

1.3

1.3

18

21

1.2

1.5

1.6

213

138

1.3

1.5

1.6

TABLE 65 Condensed

Comparison of the average length of the inner and outer pillar-cellswithout

head.

AVERAGE LENGTH OF PILLAR CELLS

AVERAGE AGE

AVERAGE BODY

WITHOUT HEAD

RATIOS OF INNER

\V V T ( ' H T

TO OUTER

Inner

Outer

days

grams

1

5

29

26

1 :1.0

8

11

35

34

1.0

18

21

48

68

1.4

213

13S

50

69.

1.4

pillar cells are smallest in man and in the rat and alike in the other two forms, Retzius ('84). Hensen ('63) states that in the base of the human cochlea both pillar cells are equally long. Later, Pritchard ('78) supported this observation. In the literature, however, no one except these two authors report the inner and outer pillar cells in the base of the adult cochlea as equal in length, but the inner is always stated to be shorter than the outer. We may therefore say that most authors agree that the inner pillar cells are at earlier stages longer than the outer, then they become equal, and finally the outer surpass the inner.

TABLE 66

Lengths of inner and outer pillars in several mammals according to different authors.

Measurements in n

INNER PILLAR

OUTER PILLAR

Authors

Animals

Basal turn

Middle

Apical

Av.

B.

M.

A.

Av.

Ratio

Corti

Mammals

30

30

34

31

4549

54 58

69

57

1:1.8

Hensen

Man

48

86 (Hamul us)

48

98 (Hamulus)

Ret zius

Wada

Rabbit

56

60

60

59

75

110

95

93

l.

Cat

41

54

57

51

68 62

95

89

84

1.6

Man

48

68

70

62

100

103

88

l.t

Albino rat after 20 days

I 41

II 45

III

54

IV

59

50

I 52

II 64

III

78

IV

84

70

-.1.4

16. Inner and outer hair cells. For a long time the inner and the outer hair cells have been regarded as the most important elements in the papilla spiralis. As these sense cells have a delicate histological structure which is readily altered, the systematic study of their growth, especially after the appearance of hearing, is a difficult matter. Though there are some observations on the length of these cells, detailed studies on their growth have not been made heretofore. I have therefore endeavored to follow the changes of their size during the postnatal period. It is first necessary to determine the form of these cells. They are generally described as cylindrical, but this description is inexact. Moreover, the inner and outer hair cells are somewhat different in shape. The former has on the surface a large oval terminal disk, which is wide hi the spiral and narrow in the radial direction. This narrows downwards to a thinner neck which expands into the broader body and terminates in a more or less round but somewhat pointed irregular end.

94

Chart 33 The weighted volume of inner and outer hair cells combined, and of their nuclei in cubic micra, tables 67 and 69.

- Weighted volume of inner and outer hair cells combined. Weighted volume of nuclei of inner and outer hair cells combined.

The outer hair cells have a much more cylindrical form, their upper terminal disk is not so wide and not round, but hexagonal. They become a bit thin in the neck, then wide in the body. Their lower end is rounded. In order, however, to determine the cell volume, the cell form has been taken as that of a cylinder. For computation, the average of the diameters measured in three places, the end disk, neck, and cell body, was taken as the diameter and the length of the cell as the length of the cylinder. From these data the volume of the cylinder was computed.

In table 67 are given the values for the volume of the cell bodies in the (1) inner and (3) outer hair cells separately and the weighted volume of both cells (in the radial section of the rat cochlea we see one row of inner and three rows of outer hair cells), according to age.

TABLE 67

Average volumes of the inner and outer hair cells in cubic micro (charts 33 to 37)

AGE

INNER HAIR CELL

OUTER HAIR CELL

BODY WGHt

Tu

I

rns of II

the o III

achlea IV

fit Average

T I

urns o II

f the ( III

iwlilr;

IV

l M 3 Average

WEIOHTD AVERAGE VOLUME

days 1

gms 5

1255

982

832

631

925

641

626

505

359

533

631

3 6 ' 9 12 15 20

8 11 10 13 13 29

1457 1374 1451 1553 1598 1627

1367 1451 1734 1812 1618 1764

1206 1549 1994 1910 1902 1972

913 1221 2013 2157 2128 2189

1236 1399 1798 1858 1812 1888

767 1047 914 818 815 894

928 967 1308 1210 1178 1215

867 1053 1459 1602 1595 1606

571 800 14^8 1499 1559 1960

783 967 1277 1282 1287 1419

896 1075 1407 1426 1418 1536 1293

Av. 11

14

1510

1624

1756

1770

1665

876

1134

1364

1303

1169

25 50 100 150 257 366 546

36 59 112 183 137 181 255

1540 1497 1353 1362 1345 1290 1266

1655 1611 1550 1497 1524 1561 1486

1909 1821 1744 1683 1738 1817 1772

1995 1924 2018 1917 1976 2297 2257

1775 1713 1666 1615 1646 1741 1695

834 805 837 832 873 893 831

1243 1204 1306 1150 1230 1239 1336

1539 1580 1510 1803 1555 1651 1650

1702 1906 1737 1917 1927 1844 1839

1330 1374 1348 1426 1396 1407 1414

1441 1459 1428 1473 1459 1491 1484

Av. 213

138

1379

1555

1783

2055

1693

844

1244

1613

1839

1385

1462

Ratios 1- 12 days 1- 20 " 1-546 " 20-546 " 1- 11 " 11-213 "

1 :2.0

2.0

0^9

1 :2.4

2.7

2.7

2!2

1 :2.3

2.4

2.4

0.9

2.0

At first we shall consider the weighted volume for the cell bodies of the inner and outer hair cells combined (chart 33). As table 67 shows, the volume increases continuously to the full size at twenty days. From one to twelve days the increase is rapid, and after that the volumes are about the same, though somewhat fluctuating. The ratios show this relation clearly.

Condensing all age groups into three (averages in table -67), then the relation changes somewhat. From one to eleven days the volume increases more than 100 per cent, while from eleven to 213 days it increases only 13 per cent.

Chart 34 The volume of inner hair cells and of their nuclei, tables 67 and 69.

Volume of inner hair cells. Volume of nuclei of inner hair cells.

The data for the growth of the nuclei of the inner and outer hair cells are presented in tables 68 and 69. The weighted values for the diameters of the nuclei (table 68) are large at the earlier stages, but from twelve days decrease gradually till old age. In the three condensed age groups (averages) we see the decrease of the values from birth till old age. In table 69 are given the values for the volumes of the nuclei, calculated as spheres (chart 33).

Chart 35 The volume of inner hair cells, according to the turns of the cochlea, table 67.

The weighted values for the volumes of the inner and outer hair cells in each turn are given in [A 3 table 70. At the bottom of each column is given the ratio from 1 to 12, 1 to 20, 1 to 546, and 20 to 546 days of age. While the volume at birth is largest in turn I and smallest in turn IV, that in turn III is largest at

Chart 36 The volume of outer hair cells and of their nuclei, in cubic micra, tables 67 and 69.

Volume of outer hair cells.

._. Volume of nuclei of outer hair cells.

six days. After nine days the volume increases always from base to apex.

Comparing the weighted vo'ume in each turn according to age, we find that the rate of increase in volume is smallest in turn I (1.3 to 1.2) and largest in turn IV (3.9 to 4.6) (table 70).

In table 72 are given the weighted values for the diameters of the nuclei of the inner and outer hair cells in each turn. They increase and then decrease during the first twelve days. The rate of decrease is largest in turn I, and smallest in turn IV, as the ratios at the bottom of each column show. That the diameters at

Chart 37 The volume of outer hair cells, according to the turns of the cochlea, table 67.

the later ages have about the same value in each turn, or are a little larger in the upper than in the lower turn, is to be seen in table 73.

TABLE 68 Mean diameters of the nuclei of the inner and outer hair cells in M

DIAMETERS NUCLEI OF THE

DIAMETERS NUCLEI OF THE

INNER HAIR CELLS

OUTER HAIR CELLS

WEIGHT

AGE

BODY

wght

Turns of the cochlea ju

Turns of the cochlea M

ED AVERAGE

I

II

ill

IV

Average

I

II

ill

IV

Average

days

gms.

1

5

8.6

8.3

7.8

7.8

8.1

7.7

8.1

7.4

7.6

7.7

7.8

3

8

8.6

8.5

8.2

7.8

8.3

8.3

8.4

8.J

7.5

8.1

8.2

6

11

8.5

8.6

8.3

8.0

8.3

8.0

8.0

8.1

7.9

8.0

8.1

c

10

8.7

8.5

8.2

8.7

8.5

76

7.9

8.4

8.2

8.0

8.1

12

13

7.6

7.7

7.5

7.9

7.7

5.8

6.5

6.8

7.4

6.6

6.9

15

13

7.5

7.5

7.7

7.9

7.6

6 1

6.6

6.8

7.0

6.6

6.9

20

29

7.0

7.3

7.6

7.8

7.4

6.0

6.4

6.9

7.3

6.6

6.8

Av. 11

14

8.0

8.0

7.9

8.0

8.0

7.0

7.3

7.5

7.6

7.3

7.5

25

36

7.3

7 2

7.2

7.1

7.2

6.0

6.3

6.3

6.5

6.3

6.5

50

59

7.0

75

7.3

7.3

7.3

6.0

6.2

6.3

6.7

6.3

6.6

100

112

6.7

7.0

7.1

7 1

7.0

5.8

6.0

6.0

6.0

5.9

6.2

150

183

6.6

6.8

7.0

7.3

6.9

6.0

6.0

6.2

6.1

6.0

6.2

257

137

6.6

6.9

7.0

7.7

7.0

5.9 16.0

6.2

6.4

6.1

6.3

366

181

7.6

7.4

7.3

7.2

7.4

5.9

6.0

6.1

6.0

6.0

6.4

546

255

6.5

6.5

6.5

7.1

6.6

5.8

6.0

6.1

6.4

6.1

62

Av. 213! 138

6.9

7.0

71

7.3

7.1

5.9

6.1

6.2

6.3

6.1

6.3

Ratios 1- 12 days

1:1. 0,|

1 :0.9|| 1 :0.9

1- 20 "

0.9

0.9 :0.9

1-546 "

0.8

O.S 0.8

20-546 "

0.9 |

0.9 :0.9

TABLE 69 Average volumes of the nuclei of the inner and outer hair cells (charts 33, 34 and 36)

AGE

BODY WEIGHT

VOLUME OF NUCLEUS HAIR CELLS

Inner Outer

WEIGHTED VOLUMES INNER AND OUTER HAIR CELLS

days

gms.

M'

M

M 3

1

5

278

239

248

3

8

299

278

289

6

11

299

268

278

9

10

322

268

278

12

13

239

151

172

15

13

230

151

172

20

29

212

151

165

25

36

195

131

144

50

59

204

131

151

100

112

180

108

125

150

183

172

113

125

257

137

180

119

131

366

181

212

113

137

546

255

151

119

125

Ratios 1- 12 days 1- 20 " 1-546 " 20-546 "

1 :0.9

0.8

0.5

0.7

0.6

0.6

0.5

0.8

0.7

0.7

0.5

0.8

100

GROWTH OF THE INNER EAR OF ALBINO RAT

101

The growth of the inner hair cell. The volume of the inner hair cell table 67 (chart 34) increases with age up to twenty

TABLE 70

Weighted volumes of the inner and outer hair cells according to the turns of the

cochlea

AGE

BODY WEIGHT

TURNS OF THE COCHLEA M*

I

II

ill

IV

days

gms.

1

5

795

715

587

427

3

8

940

1038

952

657

6

11

1129

1088

1177

905

9

10

1048

1415

1593

1574

12

13

1002

1361

1679

1664

15

13

1011

1288

1672

1701

20

29

1052

1352

1698

2017

25

36

1011

1346

1632

1775

50

59

978

1306

1640

1911

100

112

966

1367

'1569

1807

150

183

965

1237

1773

1917

257

137

991

1304

1601

1939

366

181

992

1320

1693

1957

546

255

940

1374

1681

1944

Ratios 1- 12 days

1 : 1.3 1

1.9

1 :2.9

1 :3 9

1- 20 "

1.3

1.9

2.9

4.7

1-546 "

1.2

1.9

2.9

4.6

20-546 "

0.9

1.0

1.0

1.0

TABLE 71 Condensed

Ratios of the weighted volumes of the inner -and outer hair cells according to the turns

of the cochlea

BATI08 BETWEEN TURNS

AGE

BODY WEIGHT

I-II

i-ni

I-IV

days

0ms.

1

5

1 :0.9

1 :0.7

1 :0.5

8

11

1.2

1.3

1.2

18

21

1.3

1.6

1.8

213

138

1.4

1.7

1.9

days; to nine days rapidly, then slowly. After twenty days it decreases slowly, as do the weighted volumes of the inner and outer hair cells, and with fluctuations, is nearly the same after

102

ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

100 days. The three condensed age groups show that from 1 to 11 days it has increased 80 per cent, while from 11 to 213 days it has gained less than 2 per cent.

TABLE 72

Weighted diameters of the nuclei of the inner and outer hair cells according to the

turns of the cochlea

AGE

BODY WEIGHT

TURNS OF THE COCHLEA M

I

II

ill

IV

days

gms.

1

5

7.9

8.2

7.5

7.7

3

8

8.4

8.4

8.1

7.6

6

11

8.1

8.2

8.2

7.9

9

10

7.9

8.1

8.4

8.3

12

13

6.3

6.8

7.0

7.5

15

13

6.5

6.8

7.0

7.2

20

29

6.3

6.6

7.1

7.4

25

36

6.3

6.5

6.5

6.7

50

59

6.3

6.5

6.6

6.9

100

112

6.0

6.3

6.3

6.3

150

183

6.2

6.2

6.4

6.4

257

137

6.1

6.2

6.4

6.7

366

181

6.3

6.4

6.4

6.3

546

255

6.0

6.1

6.2

6.6

Ratios 1- 12 days

1 :0.8

1 :0.8

1 :0.9 1

1.0

1- 20 "

0.8

0.8

0.9

1.0

1-546 "

0.8

0.7

0.8

0.9

20-546 "

1.0

0.9

0.9

0.9

TABLE 73. Condensed

Ratios of the weighted diameters of the nuclei of the inner and outer hair cells according to the turns of the cochlea

RATIOS BETWEEN TURNS

AVERAGE AGE

AVERAGE BODY

WEIGHT

I-II

i-m

I-IV

days

gms.

1

5

1 :1.0

1 0.9

1 1.0

8

11

1.0

1.0

1.0

18

21

1.0

1.1

1.1

213

138

1.0

1.0

1.1

From nine days on the volume of the inner hair cell increases in passing from the base to the apex. During the earlier stages

GROWTH OF THE INNER EAR OF ALBINO RAT

103

there are some fluctuations (table 67, chart 35). In the condensed table 74 the general relations are shown. The growth of the nuclei of the inner hair cells in diameter is given in table 68. As we see, the diameters increase from birth to nine days, then decrease slowly but steadily. In the three average age groups, however, the values decrease continuously with age. In table 69 are given the values for the volumes of the nuclei of the inner hair cell (chart 34).

TABLE 74 Condensed Ratios of the volume of the inner hair cells according to the turns of the cochlea

RATIOS BETWEEN TURNS

AVERAGE AGE

AVERAGE BODY

WEIGHT

I-II

i-in

I-IV

days

grams

1

5

1 0.8

1 0.7

1 0.5

11

14

1.1

1.2

1.2

213

138

1.1

1.3

1.5

TABLE 75 Condensed

Ratios of the diameters of the nuclei of the inner hair cells according to the turns of the cochlea

RATIOS BETWEEN TDRN8

AVERAGE AGE

AVERAGE BODY

WEIGHT

I-II

I-II I

I-IV

days

grams

1

5

1 1.0

1 :0.9

1 0.9

11

14

1.0

1.0

1.0

213

138

1.0

1.0

1.1

The ratios of the diameters of the nuclei of the inner hair cells decrease at the earlier ages in each turn from the base to the apex. After nine days they are nearly the same in all the turns (tables 68 and 75), though their absolute values decrease in all the turns after nine days.

The growth of the outer hair cells. In general, the changes in the volume of the outer hair cells are like those in the inner hair cells. Therefore, the volume increases strikingly up to nine days of age, then gradually to twenty days. The main difference is that the volume in the outer hair cells does not diminish so much after twenty-five days, but holds nearly the same value (table 67, chart 36). In condensed age groups, therefore, we see a large increase in the size of the cells with age.

To determine the growth of the outer hair cells in each turn of the cochlea, table 67 is used (chart 37). From twenty days on the values increase from the basal to the apical turn. Before twenty days the relations are irregular or reversed. In table 76 this relation is clearly brought out.

Comparing the changes of the volume of the outer hair cells in three age groups (table 67), we find that the average volume increases throughout each turn with age, except in turn I, where

TABLE 76 Condensed Ratios of the volumes of the outer hair cells according to the turns of the cochlea

RATIOS BETWEEN TURNS

AVERAGE AGE

AVERAGE BODY

WEIGHT

I-II

i-in

I-IV

days

grams

1

5

1 1.0

1 0.8

1 0.6

11

14

1.3

1.6

1.5

213

138

1.5

1.9

2.2

that at eleven days is largest. In the inner hair cells, however, values at eleven days are largest in both turn I and II.

For the nuclei of the outer hair cells, the diameters are given in table 68). Here the d ! ameters tend to increase from one to nine days. At twelve days they decrease strikingly, and after that very slowly. In table 69 are given the values for the volumes of the nuclei of the outer hair cells.

In table 68 are given also the measurements for the nuclei of the outer hair cells according to the turn of the cochlea. At nine days and after, the diameters become larger in passing from base to apex, while in the earlier stages this relation is irregular or reversed. The decrease of the measurements in, each turn with age is clearly shown in the three age groups.

In table 77 are given the average ratios of turn I to the three other turns.

The comparison of the growth of the inner and outer hair cells. As already stated, the growth of the inner and outer hair .cells in volume proceeds in about the same way till they reach their full size at twenty days. After that we note a difference between them. While the outer hair cells maintain a nearly constant volume, the volume of the inner hair cells diminishes

TABLE 77 Condensed

Ratios of the diameters of the nuclei of the outer hair cells according to the turns of

the cochlea

RATIOS BETWEEN TURNS

AVERAGE AGE

AVERAGE BODY

WEIGHT

I-II

I-II I

I-IV

days

grams

1

5

1 1.1

1 1.0

1 1.0

11

14

1.0

1.1

1.1

213

138

1.0

1.1

1.1

TABLE 78 Condensed Comparison of the volumes of ike inner and the outer hair cells

AVERAGE VOLUMES HAIR CELLS

AVERAGE AGE

AVERAGE BODY

RATIOS OF INNER

WEIGHT

TO OUTER

Inner

Outer

days

grams

M

A

1

5

925

533

1 0.6

11

14

1665

1169

0.7

213

138

1693

1385

0.8

somewhat with age. When we consider the volume according to the three age groups, it increases in both groups throughout life (table 78). There are, however, large differences in the rate of increase. The inner hair cell increases its volume at 11 days by 80 per cent and between 11 and 213 days by less than 2 per cent. For the outer hair cells the increase by 11 days is 120 per cent and from 11 to 213 days, 19 per cent. At the same time the inner are always larger than the outer hair cells, as the ratios in table 78 show.

The diameters of the nuclei in both the inner and outer hair cells diminish in value after nine days of age. This decrease is larger in the outer than in the inner cells. In table 79 are given the values for the diameters of the nuclei in both inner and outer hah* cells. In the last column are the ratios between them.

Thus, while the volumes of the outer hair cells, as compared with the inner hair cells, become relatively larger with age (table 78), the diameters of their nuclei become relatively smaller (table 79).

TABLE 79 Condensed Comparison of the diameters of the nuclei of the inner and outer hair cells

AVERAGE DIAMETERS OF THE

AVERAGE

NUCLEI OF THE HAIR CELLS

RATIOS OF THE AVERAGE DIAMETERS OF THE NUCLEI OP

AVERAGE AGE

BODY

WEIGHT

Inner

Outer

CELLS

days

grams

M

M

1

5

8.1

7.7

1 1.0

11

14

8.0

7.3

0.9

213

138

7.1

6.1

0.9

Comparison of the growth of the inner and outer hair cells according to sex. A careful and elaborate comparison has been made to determine whether there are differences in the growth of the hair cells according to sex.

In table 80 are given the average values for the volumes of the cell bodies and their respective nuclei. No significant differences according to sex were found.

Comparison of the growth of the inner and outer hair cells according to side. The same treatment of the data was followed as in the determination for the influence of sex. In table 81 are given the average values for the volumes of the inner and outer hair cells and their respective nuclei. Again no significant differences according to side were found.

On the nucleus-plasma ratios of the inner and outer hair cells. For the inner and outer hair cells here measured the weighted volumes of the cell bodies and of their nuclei are entered in the condensed table 82, and the ratios of the volume of the nucleus to that of the cytoplasm (=cell volume less nucleus volume) are given in the last column. This ratio increases with age, as table 82 shows. While the ratio is 1.5 in the youngest and smallest group, it is 9.9 in the largest. This means that as a group these cells are continually growing in volume. This result may be analysed for the two groups of cells involved.

TABLE 80

Average volumes of inner and outer hair cells and of their respective nuclei

in n 3 according to sex

INNER HAIR CELLS

OUTER HAIH CELLS

WEIGHTED AVERAGE

Att

BODY

NO. OF

BEX

Average volume

Average volume

VOLUME

BATS

Cell

Nucleus

Cell

Nucleus

CELLS

NUCLEI

da j/5

grams

3

7

1

0*

1213

310

815

268

915

278

8

1

9

1319

310

888

322

996

319

6

11

2

tf

1426

289

955

278

1073

281

10

2

9

1372

310

979

268

1077

278

9

10

2

cT

1701

310

1351

258

1439

271

9

2

9

1895

345

1203

278

1376

295

12

14

2

c? 1

1830

258

1344

157

1466

182

12

2

9

1886

221

1221

151

1387

168

100

146

1

cT

1687

180

1342

113

1428

129

103

1

9

1779

212

1319

108

1434

184

150

189

1

rf 1

1679

165

1382

119

1456

131

154

1

9

1639

212

1611

119

1618

142

365

205

1

tf

1739

258

1389

119

1477

154

170

1

9

1659

221

1486

113

1529

140

Volume greater in male 3

2

3

4

5

3

Volume greater in female 4

4

4

2

2

4

Equal

1

1

.

The nucleus-plasma ratio of the inner and outer hair cells considered separately. This is shown for the inner hair cells in table 83. The ratios are also progressive, but somewhat larger for the earlier age groups and smaller for the oldest, than in the previous instance.

The ratios for the outer hair cells are also progressive, and the range is greater than for the inner hair cells as table 84 shows. Here the ratio is 1.2 for the youngest group and 10.6 for the oldest. This indicates that at one day and eleven days the relative volume is less in the outer than in the inner hair cells, but at the later age the outer hairs cells grow more.

TABLE 81

Volumes of the inner and outer hair cells and of their respective nuclei according

to side in ft 3

AGE

BODY WEIGHT

NO. OF

BATS

SIDE

INNER HAIR CELLS

OXJTER HAIR CELLS

WEIGHTED AVERAGE VOLUME

Average volume

Average volume

Cell

Nucleus

Cell

Nucleus

CELLS

NUCLEI

1

5

2

R.

895

299

555

248

640

261

L.

955

268

511

230

622

239

3

7

1

R.

1213

310

815

268

915

278

L.

1395

299

920

299

1039

299

6

11

2

R.

1381

322

1010

278

1103

289

L.

1416

289

923

258

1046

268

9

9

2

R.

1782

310

1177

268

1328

278

L.

1815

333

1378

268

1487

284

12

12

1

R.

1887

212

1310

151

1454

166

L.

1885

221

1132

151

1320

168

15

13

1

R.

1895

230

1522

144

1615

165

L.

1848

239

1419

151

1526

172

20

29

2

R.

1914

212

1365

144

1502

161

L.

1862

221

1472

165

1570

179

25

36

2

R.

1758

204

1307

131

1420

149

L.

1792

195

1351

131

1461

147

50

59

2

R.

1741

204

1443

125

1518

145

L.

1687

204

1305

137

1401

154

100

102

2

R.

1675

187

1355

113

1440

131

123

2

L.

1658

172

1339

113

1419

128

150

189

1

R.

1565

172

1420

113

1456

128

L.

1679

165

1382

119

1456

131

257

137

2

R.

1685

187

1377

125

1454

140

L.

1607

180

1416

119

1464

134

367

175

2

R.

1634

195

1436

113

1486

134

365

188

2

L.

1848

230

1374

113

1493

142

546

255

2

R.

1831

157

1474

119

1563

128

L.

1559

151

1353

119

1405

127

Volume greater on right side 7

8

9

3

7

6

Volumfe greater on left side 7

5

5

5

6

8

Equal

1

6

1

GROWTH OF THE INNER EAR OF ALBINO RAT

109

This seems to be important and to illustrate the fact that in the papilla spiralis the growth of the elements lying nearer the axis occurs earlier than that of the elements nearer the periphery.

TABLE 82 Condensed Nucleus-plasma ratios of the inner and outer hair cells M*

AVERAGE AGE

AVERAGE BODY WEIGHT

AVERAGE VOLUME OF INNER AND OUTER HAIR CELLS

VOLUME OK CYTOPLASM

NUCLEUSFLA8MA RATIOS

Cell

Nucleus

days

1

11

213

grams 5 14 138

631 1293 1462

248 226 134

383 1067 1328

1 : 1.5

4.7:9.9

TABLE 83 Condensed Nucleus-plasma ratios of the inner hair cells /**

AVERAGE AGE

AVERAGE BODY WEIGHT

AVERAGE VOLUME OF 1XXER HAIR CELLS

VOLUME

or

CYTOPLASM

NUCLEUSPLASMA RATIOS

Cell

Nucleus

days 1 11 213

0ms.

5

14 138

925 1665 1693

278 268 187

647

1397 1506

1 2.3 5.2 8.1

TABLE 84 Condensed Nude us- plasma ratios of the outer hair cells

AVERAGE AGE

AVERAGE BODY WEIGHT

AVERAGE VOLUME OF OUTER HAIR CELLS

VOLUME or

CYTOPLASM

NUCLEUSPLASMA RATIOS

Cell

Nucleus

days 1 11 213

grams 5 14 138

533 1169 1385

239 204 119

294

965 1266

1 1.2

4.7 10.6

17. Deiters' cells. The Deiters' cells are most delicate elements. In the literature, so far as I know, there are no exact observations touching the growth of these cells in the papilla spiralis, except a few data for their length. They have an

110 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

irregular form and consist of three parts, the phalangeal process, cell body, and foot. The phalangeal process is thin, somewhat crooked in the adult though it runs straight at an earlier stage. As the boundary between this process and the cell body, we take a line running through the supporting cup ('Stutzkelch' of Held) parallel to the plane of the basilar membrane (fig. 10). The cell body in its upper part is wide, including here a round nucleus. It then becomes thin and passes over to the foot. Thus it is almost impossible to get the true volume of the cells. Therefore, we have determined the volume of the cell body only, excluding that of the phalangeal process.

We think of the cell body as a cylinder having an average diameter, which is calculated from four diameters measured at four levels. The first level is just below the upper boundary of the cell body, the second in the widest part, the third below at about the middle of the cell body, and the last is at the narrowest part near the foot. .

The height of the cylinder is the length of the cell body within the limits just noted. Thus the volume obtained approximates the value for the natural size of the cell body without the process.

In table 85 (chart 38) are given the values for the volumes of the Deiters' cells thus computed and the diameters and volumes of the nuclei according to age. As there are in the radial section three rows of cells, the values given are, of course, the average of these. At the bottom of the last column appear the ratios at 1 to 12, 1 to 20, 1 to 546, and 12 to 546 days. As we see, the volume of the cell body increases throughout life, slowly during the first nine days, but from twelve to twenty days very rapidly, and then less rapidly to old age.

While the ratio from one to twelve days is 1:5.4, that from 1 to 546 days is 1:29.1, or more than five times as large.

When we consider the volumes of the cells in each turn of the cochlea, we see that it is smallest in turn I and largest in turn IV, though there are some exceptions before nine days of age. Table 86 shows these relations.

The diameters of the nuclei of the cells grow, after some fluctuations in the values at earlier stages, very slowly to old

GROWTH OF THE INNER EAR OF ALBINO RAT 111

age, as indicated in table 85 and chart 38. The ratios at the bottom of the corresponding column show these relations. The values for the volumes of the nuclei of the cells are given in the last column. Here, also, the diameters in the upper turns tend to be larger than in the basal turn. In table 87 are given the ratios of the diameters of turn I to the three other turns. We see in all the turns about the same ratios, 1:1.0.

In the literature we find but two observations on the diameters of the nuclei of the Dieters' cells. Kolmer ('07) reports hi the pig 5 [i, and von Ebner ( '02) gives in man 7 (x for the diameter of the round nucleus of the cells.

In the rat, therefore, the diameter is larger than in these two forms, but no significance can be attached to this difference until correction has been made for the several techniques employed. This I am unable at present to do.

On the nucleus-plasma ratio in Deiters 1 cells. In the condensed table 88 are given the volumes of the cell bodies and of their nuclei together with the respective nucleus-plasma ratios. This shows that the ratio is progressive with age. While the ratio is at birth only 0.05, that in the oldest group is 28.3. The absolute increase is not great at earlier stages, but by eighteen days it is marked

The rapid change in the ratio is very interesting. Before eight days of age the cells are still immature. Some time after eight days they develop rapidly, seeming to play some important part in the special functions of the cochlea.

On the length of Deiters' cells. To measure the length of Deiters' cells we divide them into two parts, the upper and the lower, by the boundary line between the cell body and the phalangeal process. The sum of these two lengths makes the total length of the cells.

In table 89 are given the values for the total length and for each part separately (chart 39). As in the volume of the cells, we see an astonishing change in the development of the length. The length of the cells increases through life, at earlier stages a little, but at twelve days it becomes nearly twice as long as at nine days. The ratios at the bottom of the last column show the course of growth.

TABLE 85

The volume of Deiters' cells and the mean diameters and volumes of their respective nuclei (chart 38)

VOLUME OF THE DEITERS* CELLS

1

NUCLEI

VOLUMES

BODY

fit

Diameters

AGE

WEIGHT

Average

I

II

III

IV

Average

I

II

III

IV

diam

Average

volume

eters

volumes

M

M

days

grams

1

5

278

232

237

256

251

7.6

7.5

7.5

8.1

7.7

239

3

8

290

309

349

352

325

7.0

7.0

6.9

7.0

7.0

180

6

11

425

395

495

364

420

7.0

6.5

6.7

6.6

6.7

165

9

10

635

461

554 423

518

6.9

7.0

7.1

7.1

7.0

180

12

13

1122

1369 1395

1569

1364

6.5

7.0

6.9

7.1

6.9

180

15

13

1466

2187 2659

3127

2359

7.0

7.2

7.2

7.3

7.2

195

20

29

3576

427115740

6171

4939

7.6

7.8

7.9

7.9

7.8

248

25 50

36 59

4088 4467 5470 4839 5970 6258

5757 6816

4695 5971

7.3 7.3

7.2 7.5

7.3

7.5

7.4 7.4

7.3 7.4

212 212

100

112

5011

6083

7137 6607

6210

6.9

7.6

7.5

7.4

7.3

212

150

183

5755 6291 7657

6750

6613

7.5

7.6

7.5

7.1

7.4

212

257

137

5776 6540 8841

8544

7425

7.4

7.8

7.9

8.0

7.8

248

366

181

6163

6908

7701

7895

7167

7.4

7.7

7.9

7.9

7.7

248

546

255

6092 6919 8028

8152

7298

7.4

7.9

8.0

7.7

7.7

248

Ratios 1 12 days

1 5.4

1 0.9

1 20 "

19.7

1.0

1546 "

29.1

1.0

12546 "

5.4

!

1.1

TABLE 86 Condensed Ratios of volumes of the Deiter's cells according to turns of the cochlea

RATIOS BETWEEN TURNS

AVERAGE AGE

AVERAGE BODY

WEIGHT

I-II

i-m

I-IV

days

grams

1

5

1 :0.8

1 :0.9

1 :0.9

8

11

1.0

1.1

1.1

18

21

1.3

1.7

1.8

213

138

1.1

1.4

1.3

TABLE 87 Condensed Ratios of the diameters of the nuclei of Deilers' cells according to turns of the cochlea

RATIOS BETWEEN TURNS

AVERAGE AGE

AVERAGE BODY

WEIGHT

I-II

I-III

I-IV

days

grams

1

5

1 1.0

1 1.0

1 : 1.1

8

11

1.0

1.0

1.0

18

21

1.0

1.0

1.0

213

138

1.0

1.1

1.0

112

GROWTH OF THE INNER EAR OF ALBINO RAT

113

90OO

8OOO

7OOO

6000

5000

4000

3OOO

2OOO

1OOO

AGE

o

25

50

50 1OO 2OO 300 4OO 5OO

Chart 38 Showing the volume of Deiters' cells and their nuclei, on the average and according to the turns of the cochlea, table 85. Average volume of Deiters' cells.

._. Volume of the cells in about the middle of the basal turn.

Volume of the cells in about the beginning of the middle turn.

Volume of the cells in about the middle of the middle turn.

Volume of the cells in about the beginning of the apical turn.

Average volume of nuclei of Deiters' cells, X 10.

Comparing the length of the cells according to the turn of the cochlea, we find that after twelve days the length increases from the base to the apex, in turn III very rapidly, in turn IV gradually (table 90). At earlier stages the relations are irregular.

TABLE 88 Condensed Nucleus-plasma ratios of the Deiters' cells

AVERAGE VOLUMES

VOLUME OF

NUCLEUS

AVERAGE AGE

AVERAGE BODY

CYTOPLASM

PLASMA RATIOS

WEIGHT

Cell

Nucleus

.M

M

M

days

grams

1

5

251

239

12

1 : 0.05

8

11

657

172

485

2.8

18

21

3649

221

3428

15.5

213

138

6483

221

6262

28.3

TABLE 89

Length of cell body and of processus phalangeus of Deiters' cells p (chart 39)

LENGTH OF THE CELL BODY

LENGTH OF THE PROCESSUS

PHALANGEUS

TOTAL

BODY

LENGTH

AGE

WEIGHT

Turns of cochlea

Turns of cochlea

OF THE

CELLS

I

II

III

IV

Average

I

II

ill

IV

Average

days

gms

1

5

8

8

8

9

8

20

19

20

15

19

27

3

8

8

9

9

10

9

16

17

18

18

17

26

6

11

9

9

11

10

10

19

22

23

22

22

32

9

10

18

12

13

11

14

18

21

26

24

22

36

12

13

31

35

40

43

37

18

22

29

25

24

61

15

13

34

37

40

43

39

21

25

32

31

27

66

20

29

39

41

49

49

45

19

23

30

34

27

72

25

36

42

43

51

51

47

17

21

30

32

25

72

50

59

41

45

53

53

48

16

22

30

34

26

74

100

112

43

45

54

53

49

17

25

29

31

26

75

150

183

45

46

53

52

49

17

22

32

34

26

75

257

137

43

46

56

58

51

18

24

28

31

25

76

366

181

43

48

55

55

50

17

23

29

32

25

75

546

255

46

49

56

56

52

16

23

30

33

26

78

Ratios 1 12 days

1 :4.6

1 :1.3

1 :2.3

1 20 "

5.6

1.4

2.7

1546 "

6.5

1.4

2.9

12546 '"

1.4

1.1

1.3

When we consider the length of the cell body, it is remarkable that the increase takes place so rapidly. While at 1 day it measures only 8 (x and at nine days only 14 ji, it increases very suddenly at twelve days of age, and after that slowly but continuously (table 89).

TABLE 90 Total length of Deiters' cells according to turns of the cochlea (chart 39)

AGB

BOOT WEIGHT

TURNS OF THE COCHLEA

I

II

III

IV

days

grams

1

5

28

27

28

24

3

8

24

26

27

28

6

11

28

31

34

32

9

10

36

33

39

35

12

13

49

57

69

68

15

13

55

62

72

74

20

29

58

64

79

S3

25

36

59

64

81

83

50

59

57

67

83

87

100

112

60

70

83

84

150

183 '

62

68

85

86

257

137

61

70

84

89

366

181

60

71

84

87

546

255

62

72

86

89

80 M 60

40

20 n

Chart 39 The length of Deiters' cells, tables 89 and 90.

500

Total length of the cells. Length of the cell bodies. Length of processus phalangeus.

In the ratios at the bottom of table 89 this is shown very evidently and in each turn this relation is to be seen.

For the length of the phalangeal process the story is quite different. It increases from birth to twelve days a little; at fifteen days it reaches full size, and then holds its value (table 89) . After three days the length is smallest in turn I and largest in turn IV. This relation lasts to old age.

Comparing the growth of the length of the cell body and phalangeal process, there is a large difference between them. While the length in the phalangeal process is at birth over twice that of the cell body, at 546 days it is only half that of the cell

TABLE 91

Total length of Deiters' cells in fj, (Retzius)

AGE

RABBIT

CAT

Basal

Middle

Apical

Average

Basal

Middle

Apical

Average

turn

New-born

48

70

60

59

45

65

48

53

2

45

66

54

55

1

3

45

60

7

80

90

75

82

49

69

63

60

10

98

100

114

104

11

75

90

45

70

14

84

105

112

100

30

54

75

70

66

body. Thus the increase of the total length of Deiters' cells is due chiefly to the increase in the length of the cell body.

Retzius ('84) gives the length of Deiters' cells in the rabbit and cat as in table 91.

Table 91 shows that in both the rabbit and the cat the length at all ages is greater, and especially at the earlier stage is twice as great, as in the rat. In the rabbit there is a rapid increase in length between seven and ten days. For the cat the values are smaller, nearer those of the rat, and show less change between birth and thirty days.

18. Summary and discussion. Using the foregoing data on the form and measurements of the elements of the cochlear duct, I desire here to summarize the results and to discuss the consequent changes in the form of the organ of Corti (table 92).

We have already noted that at birth the greater epithelial ridge constitutes the main part of the tympanic wall, and the lesser epithelial ridge, from which arises later the most important organ, is represented by a small and undeveloped prominence. With age this greater ridge disappears gradually and is transformed into a furrow lined with low epithelial cells, the sulcus spiralis internus (Waldeyer). These changes appear first at the base and then pass gradually to the upper turns. In the lesser ridge also there are important developmental changes. At first the hair cells and pillar cells grow, and just before the special function appears, striking changes are seen in Deiters' and Hensen's cells. These increase, especially in their length, very rapidly.

Thus the papilla spiralis, which hitherto had its highest point at the summit of the arch of Corti, shows a remarkable change of form, as the outer part of the papilla increases its height, so that finally Hensen's cells mark the highest point in the papilla. The surface then ceases to be parallel to the basilar membrane, and slopes inward, making with the basilar membrane an acute angle opening outward. At the same time the papilla spiralis appears to be shifted inward i.e., towards the axis.

Kolliker has described how the cells, from which the pillars or rods of Corti arise, at first stand nearly parallel, but later separate at their base. He thought that this "von einem Langenwachstum (?) der Zellen selbst oder ihrer Grundlage, der Membrana basilaris, abhiingen kann. "

Hensen ('63) first studied this interesting problem in the ox and found it to depend on a peculiar process. He regarded the inward migration as taking place chiefly in the inner pillar cell. The outer pillar cell in the upper turn moves somewhat outward ; in the base, however, inward. Moreover, the outer pillar cell increases its length during the development of the papilla much more than the inner does. Thus the summit of the arch of Corti and therefore the papilla spiralis shifts inward on the basilar membrane.

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41

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Radial distance betw habenula perforata Breadth of membran! (table 9)

Breadth of membran (table 4)

Thickness (table 4)

jj

1

|i

/. -_

3

From hab. perf. to 01 Distance between thi

5 5

-M

c/.

s

O & & g ^J - J3 X! -r=

iiilliiill

^ " S S^

O W (JrJ W

GROWTH OF THE INNER EAR OF ALBINO RAT

119

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oo t^ co co t o co m coo ^w

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^"00 I-H <M 1-1 O

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I'Mg 2? W V v Ja V V

i- S || a a L|SSl3S

HI C~" WH < C/2

120

Bottcher ( '69. 72) disagreed with Hensen, though he has confirmed, as did Middendorp ('67), the striking inward spreading of the base of the inner pillar cell.

Gottstein] ( 72) held that the inner pillar cell does not move inward, but that the increase in the length of the labium tympanicum may explain the peculiar approach of the habenula perforata to the arch of Corti.

Retzius ('84) agreed in general with Hensen 's assertion that in the course of development the surface of the sense organ comes to lie under the basal surface of the membrana tectoria. He thought that this change of position is brought about "weniger in dem Verhalten der Pfeilerzellen, sondern vor allem in dem starken Wachstum der Deitersschen Zellen und der von aussen andriickenden Hensenschen Stiitzzellen, ' and that, further, "vielleicht die Membrana tectoria selbst durch eigenes Wachstum und durch Vergrosserung des Limbus mit seinem Vorspriingen" contributes to this.

Held ('09) agrees with Hensen on the whole.

Prentiss ('13, p. 450) denies the wandering of the spiral organ as follows: There is no necessity for, and my preparations afford no proof of, an inward shifting of the spiral organ and a consequent displacement of the membrana tectoria "

Hardesty ('15, pp. 60 and 61) discussed the relative position of the spiral organ with reference to the basal surface of the tectorial membrane and says " the developed spiral organ acquires its position well under the basal surface of the tectorial membrane almost entirely by being carried axisward during the completion of the membrane." "In the apical turn, where these changes are greatest, the hair cells of the organ may be carried axisward a distance nearly half the width of the membrane. The upgrowth of the outer supporting cells also forces axisward the apical ends of the elements of the spiral organ and in this way contributes a small part to the shift in the relative position of the hair cells. A slight increase in width of the vestibular lip of the spiral limbus may contribute a still smaller part by extending the membrane outward."

GROWTH OF THE INNER EAR OF ALBINO RAT 121

I obtained from the measurements given in the tables the following results concerning the position of the papilla spiralis under the basal surface of the tectorial membrane.

As already stated, since the habenula perforata may be considered after birth as a punctum fixum (Hensen), it is found that the inner pillar cell shifts inward at its inner basal corner during the earlier stage of life. At six days of age it almost always reaches the habenula perforata in the basal turn, though not yet in the apical. At nine days there is no distance between the- habenula perforata and the inner corner of the inner pillar cell.

Gottstein's assumption (no measurements) that the labium tympanicum grows outward and approaches to the arch of Corti is not applicable to the rat, as shown by my tables.

The outer pillar cell also moves outward in all the turns through life, but only slightly after nine days. This result does not agree with that of Hensen ('63), who found in the ox the outer pillar cell to move inward a little at the base, not at all in the middle turn and outward at the apex. Bottcher 's outward movement of the outer pillar cell at the hamulus in the cat is 90 y. and much larger than in the rat.

Contrary to Hensen, Retzius ('84) also finds in the rabbit an outward movement of the base of the outer pillar cell throughout all the turns. On the other hand, during the earlier stages of development, the top of the arch of Corti moves outward from the labium vestibulare through the outward pressure of the greater epithelial ridge. At this stage the main part of the membrana tectoria does not yet reach to the sense cells, though the part produced from the lesser epithelial ridge spans the spiral organ and connects with the outer part of the papilla.

After nine days of age the condition of the organ is quite different. The most remarkable anatomical changes from the earlier condition are the rapid increase in the length of the outer pillar cells, in the height of the pillar cells above the basilar membrane, in the height of the papilla spiralis at the third series of the outer hair cells, in the height of Deiters' cells, and in the height of Hensen 's supporting cells. Also the tunnel of Corti appears.

The greater epithelial ridge has already disappeared in large part and been replaced by a furrow. Pressure displacement of tissue in the direction of the least resistance is common in organogenesis. Thus the inner pillar cell is subject to pressure by the rapid growth of the outward lying and greater part of the papilla spiralis and moves in the direction of the least resistance, therefore inward; the head most and the base not at all. As shown in table 44, the rapid decrease in the radial distance between the labium vestibulare and the head of the inner pillar cell is very evident. The arch of Corti changes its form, now inclining inward, instead of outward as heretofore. The lamina reticularis runs not parallel to the basilar membrane, but ascends outward. The tunnel of Corti also changes more or less its form. Nuel 's space now appears possibly as a result of this displacement of the papilla spiralis. Thus we see a change in the position of the sense organ with reference to the membrana tectoria.

With the inward shifting of the papilla, the hair cells come under the basal surface of the membrana tectoria. It is probable that the increase of the relative length of the membrane also takes part in this, since the increase in the breadth of the inner zone of the membrana tectoria from one to twelve days is as 1:3.4 (table 4), while the increase in the breadth of the basilar membrane is as 1:0.5 during the same interval (table 7).

Prentiss' ('13) statement that an inward shifting of the papilla spiralis and a consequent displacement of the membrana tectoria does not take place (in the pig) is not applicable to the rat.

In the rat the labium vestibulare and the inner edge of the head of the inner pillar cell are also two definite points in the same sense, and using them we see an inward shifting of the organ of Corti. I imagine that his observation may have misled him, since the tectorial membrane arises in his preparations from both greater and lesser epithelial ridges, and from the earlier stages covers with its outer part the papilla spiralis. Thus the shifting of the organ inward does not necessitate a change in the position of the papilla with reference to the membrane. In his study of the tectorial membrane in the same animal (pig) , Hardesty ( ' 13) describes a large displacement of the papilla spiralis inward.

According to him, the shifting of the organ consists of, 1, the moving axisward of the organ itself, and this constitutes the main shift; 2, the upgrowth of the outer supporting cells, and this contributes a small part to the shift, and, 3, a slight increase of the vestibular lip of the spiral limbus which may contribute a still smaller part. The relation in the rat, however, is different. The moving inward of the papilla itself is not seen in the rat. In the earlier stages the inner basal corner of the inner pillar cell alone shifts inward and reaches the habenula perforata. On the other hand, the outer pillar cell moves outward and the head of the inner pillar cell also, at earlier stages, towards the cells of Hensen. Therefore, during the earlier stages the arch of Corti moves rather outward, owing to the pressure of the growth of the greater epithelial ridge. Since the habenula perforata is to be regarded as a fixed point, the inward displacement of the head of the arch of Corti and of the papilla spiralis is not due to the active shifting inward of the organ itself, as Hardesty ('15) thinks, but to the disappearance of the greater ridge and the passive pressure exerted by the upgrowth of the outer pillar cells and Deiters' and Hensen 's cells. The vestibular lip of the spiral lamina and the tectorial membrane itself both increase in their length a little, and these increases play some part in the change of the position of the papilla spiralis with reference to the basal surface of the tectorial membrane.

The membrana basilaris is not concerned with the moving inward of the organ. It increases its length with age in all the turns, but we do not find the change in the position of the feet of the pillar cells on the membrane in such a sense that the feet move inward on it.

Thus the shifting of the papilla spiralis inward in the rat during the development takes place rather in the manner described by Retzius.

Hardesty ('15) states that in the apical turn of the cochlea the organ may be moved axisward a distance equal to about half the maximum width of the greater epithelial ridge, the maximum width of the ridge representing approximately the width of the outspanning zone of the membrane produced upon it.

No other author reports such a high degree of the inward shifting of the organ. I have not studied the pig, but in the rat I get the average distance between the labium vestibulare and the inner edge of the head of the inner pillar cell as follows (table 93).

TABLE 93

Average distance between the labium vestibulare and the inner edge of the inner pillar cell in n (albino rat)

AGE

BODY WEIGHT

TURNS OF COCHLEA

I

II

III

IV

Average

days

grams

(1) 5 (2) 154 Difference betw 1 and 2

9 102 een age groups

94

63 31

124 100 24

1,54 134 20

165

148 17

23

Therefore, in the rat the organ moves inward on the average of 23 [A; that is, in the ratio of 1:0.16 of the maximum distance between these two points. It may be noted that the difference in this table is not the same in the several turns, but diminishes from base to apex a relation which is the reverse of that reported by Hardesty ('15) in the pig. I have no explanation for these differences except their possible dependence on the different animals used.

C. On the growth of the largest nerve cells in the ganglion spirale

Observations. For the present studies the fourteen age groups used in the previous observations on the growth of the tympanic wall of the cochlear duct were employed. In order to see the relation between the growth of the papilla spiralis and the cells of the ganglion spirale, both studies were made on the same sections. In addition, however, I made cross-sections of the cochlea (i.e., at right angles to the axis) in several age groups to follow the growth and the changes in the form of the nerve cells as they appear in this plane. The data for the animals thus used are given in table 94.

For the measurement of the nerve cells a Zeiss system was used with a micrometer eyepiece, having each division equal to 2jx. Since we have in the radial vertical section of the cochlea of the rat at least four turns, there are four cell groups available in each section (fig. 3). The ten largest cells in each ganglion were measured, and thus a total of forty cells in a section were taken for the measurement of the nucleus and the cell.

We used, as stated, four cochleas in each age group, so that 160 cells were measured for each age. Also in the cross-sections the four nearly corresponding turns were used for the measure- ments, selecting the ten largest cells in each turn.

TABLE 04 Data on rals used for cross-sections of the cochlea ganglion spirale

AGE

BOOT WEIGHT

BODY LENGTH

BEX

8IDE

HEARING

days

grams

15

20

84

(?

L.

Prompt response

20

27

93

d"

L.

25

39

114

P

L.

100

95

152

<?

R.

150

169

192

9

L.

371

220

206

c?

L.

In the measurement of the cell bodies the two maximum diameters at right angles to each other were determined, and also the two corresponding diameters for the nuclei.

Here it is to be noted that the expressions turn I, II, III, and IV are used in the same sense as in the earlier chapters.

In table 95 (chart 40) are given the values for the average diameters of the cell bodies and their nuclei in the ganglion spirale in the radial vertical section according to fourteen age groups. Under 'cell body, diameter,' the first column gives the long, the second the short, and the third the computed diameter; i.e., the square root of their products. These last values ap- proximate the mean diameters of the nerve cells. At the foot of the third column are given the ratios from 1 to 20, 1 to 546, and 20 to 546 days. The values for the diameters of the nurlei are similarly given and also the ratios.

As the tables and charts show, the diameters of the cell bodies and also of their nuclei are largest at twenty days of age. After that age they diminish, gradually. While the ratio for one to twenty days is 1:1.7 in the cell bodies and 1:1.3 in the nuclei, that for 1 to 546 days is 1:1.6 and 1:1.2, respectively.

TABLE 95

Diameters of the cell bodies and their nuclei in the ganglion spirale (radial-vertica I

section) (chart 40)

Diameters in M

Cell body

Nucleus

AGE

BOOT

BODY

WEIGHT

LENGTH

Long

Short

Computed

Long

Short

Computed

days

grams

mm.

1

5

48

11.0

10.0

10.5

8.2

7.6

7.9

3

8

56

12.0

11.1

11.5

8.2

7.8

8.0

6

11

63

13.6

12.3

12.9

8.8

8.1

8.4

9

10

58

14.3

12.8

13.6

8.9

8.2

8.5

12

13

70

14.6

13.1

13.8

8.7

8.2

8.5

15

13

75

15.7

14.1

14.9

9.1

8.4

8.7

20

29

95

19.0

17.3

18.1

10.3

10.0

10.2

25

36

104

18.5

16.9

17.7

10.2

9.9

10.1

50

59

125

18.5

16.6

17.5

10.3

9.7

10.0

100

112

159

18.1

15.7

16.9

9.8

9.2

9.5

150

183

190

18.2

15.3

16.7

9.6

8.8

9.2

257

137

175

18.5

15.3

16.8

9.9

9.4

9.6

366

181

191

18.6

15.3

16.9

9.8

9.0

9.4

546

255

213

18.6

15.3

16.9

9.7

9.0

9.4

Ratios

120 days

1:1.7

1:1.3

1546 "

1.6

1.2

20546 "

0.9

0.9

In table 96 (chart 41) are a series of computed diameters of the cell bodies and of their nuclei according to the turns of the cochlea. At the bottom of each column are given the ratios from 1 to 20, 1 to 546, and 20 to 546 days. Determining the ratios for each column, it appears that in general the diameters of the cell bodies and their nuclei are largest at twenty days throughout all the turns. This increase is very considerable from fifteen to twenty days. Then they decrease very slowly till 546 days.

GROWTH OF THE INNER EAR OF ALBINO RAT

127

Table 97 enables us to compare the ratios in the diameters of the cell bodies and their nuclei in turns I, II, III, and IV in the condensed age groups. In both the cell bodies and their nuclei the ratios become slightly larger in passing from the basal toward the apical turn, except in the one day group, which it reversed.

On the comparison of the diameters of the nerve cell bodies and their nuclei in the ganglion spirale according to sex. For this comparison seven age groups were used. In each age group we have sometimes one, sometimes two cochleas of the same sex.

Chart 40 Showing the computed diameter of the largest cell bodies and their nuclei from the ganglion spirale, table 95.

---

Diameters of the cell bodies.

---

Diameters of the nuclei.

In the latter case the average value is recorded. In table 98 are given the values for these diameters, and it is plain that there is no significant difference in these values according to sex. On the comparison of the diameters of the nerve cell bodies and their nuclei in the ganglion spirale according to side. For this purpose fourteen age groups were employed. In most cases two cochleas from the same side were used in each age group. In these cases the average value is recorded. Table 99 shows the values for the diameters of the cell bodies and their nuclei accord- ing to side, but reveals no evident difference in this character.

On the morphological changes in the ganglion cells during growth. As my sections could not be stained with thionine, my observations on the Nissl bodies are incomplete, yet the slides stained with Heidenhain's iron haematoxylin and van Gieson's stain, as well as by haematoxylin and eosin, were helpful here.

TABLE 96

Computed diameters of the cell bodies and their nuclei in the ganglion spirale according to the turns of the cochlea (chart 41 )

AGE

days

BODY WEIGHT

gms

TURNS OF THE COCHLEA

Computed diameters M

I

II

in

IV

Cell body

Nucleus

Cell body

Nucleus

Cell body

Nucleus

Cell body

Nucleus

1

5

11.0

8.0

10.8

8.2

10.4

8.0

9.6

7.4

3

8

11.5

7.9

11.5

7.9

11.7

8.0

11.3

8.1

6

11

12.9

8.4

12.6

8.2

13.0

8.5

13.3

8.6

9

10

13.4

8.4

13.4

8.5

13.6

8.6

13.7

8.6

12

13

13.6

8.1

13.5

8.1

13.8

8.6

14.7

9.0

15

13

14.8

8.6

15.0

8.6

14.6

8.6

15.0

9.2

20

29

17.6

10.0

17.6

9.9

18.1

10.2

19.0

10.4

25

36

16.9

9.9

17.6

10.0

17.6

10.1

18.4

10.3

50

59

17.2

9.7

17.2

9.7

17.6

10.0

17.9

10.1

100

112

16.9

9.6

16.9

9.4

16.3

9.3

16.9

9.6

150

183

16.9

9.3

16.3

9.0

16.6

9.1

17.0

9.1

257

137

16.7

9.6

16.7

9.4

16.9

9.7

17.0

9.7

366

181

16.7

9.3

16.4

9.2

16.7

9.1

17.7

9.7

546 255 Ratios 1 20 day* 1546 " 20546 "

15.8 1:1 .6

9.2 1:1.3

16.3 1:1.6

9.4 1:12

16.9 1:1.7

9.4 1:1.3

17.4 1:2 .0

9.5 1:14

1 5

1 2

1 5

1 2

1 7

1 2

1 8

1 3

1.0

0.9

0.r-

1.0

0.?'

0.9

O.S

0.9

TABLE 07 Condensed Ratios of the diameters of the cells and nuclei of the ganglion spirale

AVERAGE AGE

AVERAGE BODY WEIGHT

RATIOS BETWEEN TURNS

I-II

l-lll

I-IV

Cell body

Nucleus

Cell body

Nucleus

Cell body

Nucleus

days

1

8 18 13

grams 5 11 21 138

1 :0.98

0.99

1.01

0.99

1: 1.25

1.00

1.00

0 99

1:0-95

1.01

1.01

i.OI

1 : 1 . 00

1.02

1.01

1 . 00

1 : . 87

1.03

1.04

1.04

1 :0.93

1.05

1 . 05

1.02

GROWTH OF THE INNER EAR OF ALBINO RAT

129

19 M 18

17 16 15 14 13 12

10 9

Si;

DAYSi-

i i

25

50

, oo 2OO 3OO 4OO

Chart 41 'The computed diameter of the largest cell bodies and of their nuclei from the ganglion spirale, according to the turns of the cochlea, table 96. Upper graphs: diameters of the coll bodies. Lower graphs: diameters of the nuclei of the cells.

130

Figure 13 illustrates semidiagrammatically the nerve cells in the spiral ganglion of the albino rat at 1 day and at 20 and 366 days.

The body of the ganglion cells at birth is small and has the characteristic fetal form. The cytoplasm is homogeneous and scanty and the Nissl bodies are not yet seen. The nucleus forms

TABLE 98

Comparison according to sex of the diameters of the cell bodies and the nuclei in

the ganglion spirale

AGE

BODY WEIGHT

NO. OF RAT8

SEX

COMPUTED DIAMETERS M

Cell

Nucleus

days

grams

3

7

1

&

11.4

8.0

8

1

9

11.4

8.0

6

11

2

tf

13.1

8.5

10

2

9

12.8

8.4

9

10

2

c?

13.6

8.5

9

2

9

13.5

8.6

12

14

2

c? 1

13.7

8.5

12

2 .

9

13.9

8.4

100

146

. 1

<?

17.2

9.6

103

1

9

16.9

9.4

150

189

1

d 1

16.5

9.1

154

1

9

17.1

9.1

365

205

1

d 1

16.3

9.0

170

1

9

16.7

9.1

Average male

14.5

8.7

Average f e male

14.6

8.7

Male larger than female

3

3

Female larger than male

3

2

Male and female equal

1

2

the greater part of the cell. The chroma tin is not yet well differentiated, and the so-called 'Kernfaden' are not visible.

The sharply marked nucleolus is in most cases in the central position, but sometimes located peripherally.

The cytoplasm matures rapidly. At six days the Nissl bodies appear, though they are of course, less abundant and smaller than in the later stages. The nucleus develops also and the chromatin is well differentiated. Thus the development in both the cell body and the nucleus proceeds rapidly in the earlier stage.

20 Days

13

366 Days

Fig. 13 Showing semi-diagrammatically the size and the morphological changes in the ganglion cells in the ganglion spirale of the albino rat at the age of 1, 20 and 366 days. All cell figures have been uniformly magnified 1000 diameters.

GROWTH OF THE INNER EAR OF ALBINO RAT

131

At twenty days the cell body reaches its maximum size. The Nissl bodies are large and abundant. The nucleus also attains

TABLE 99

Comparison according to side of the cell bodies and their nuclei in the ganglion

spirale

AGE

SIDE

COMPUTED I.I \ M K r Ml- ft

Cell

Nucleus

days

grams

1

5

2

R.

10.6

8.0

L.

10.4

7.8

3

7

1

R.

11.4

8.0

L.

11.5

8.0

6

11

2

R.

13.0

8.5

L.

12.9

8.4

9

9

2

R.

13.4

8.5

L.

13.7

8.6

12

12

1

R.

13.9

8.4

L.

14.0

8.4

15

13

1

R.

14.7

8.6

L.

14.8

8.5

20

29

2

R.

18.0

10 1

L.

18.5

10.2

25

36

2

R.

17.6

10.1

L.

17.7

10 1

50

59

2

R.

17.5

9.9

L.

17.5

9.8

100

102

2

R.

16.8

9.5

123

L.

17.0

9.5

150

189

1

R.

16.4

9.2

L.

16.5

9.1

257

137

2

R.

17.1

9.7

L.

16.6

9.5

367

175

2

R.

17.3

9.7

365

188

L.

16.5

9.1

546

255

2

R.

16.9

9.3

L.

16.9

9.9

Average right side Average left side Right larger than left Left larger than right Right and left equal

15.3 ir>.:j 4 8 2

9.1 '.M) 7 2 5

its maximum size at this age, though the rate of increase is slower than that for the cell body. With this increase of size the his- tological structure becomes that of the adult rat. Then, as the

132

ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

age advances, the size of both the cell body and of the nucleus slowly diminishes, while within the cytoplasm the differentiation of the Nissl bodies progresses. This relation is seen in the figure of the cell at 366 days, which shows that the absolute volume of the cell body and also of the nucleus is smaller than at twenty days.

From twenty to 366 days, gradual and progressive changes in all histological structures can be seen, though there are no sudden changes.

TABLE 100

Diameters of the cell bodies and their nuclei in the ganglion spirale in cross sections

of the cochlea (chart 4%)

DIAMETERS IN M

AGE

BODY

Cell body

Nucleus

Long

Short

Computed

Long

Short

Computed

days

grams

15

20

15.7

14.3

15.0

9.3

8.4

8.8

20

27

18.3

16.6

17.4

10.3

10.0

10.1

25

39

18.0

16.6

17.3

10.1

9.8

9.9

100

95

17.6

16.2

16.9 '

9.9

9.5

9.7

150

169

17.4

16.0

16.7

9.8

9.1

9.4

371

220

16.5

15.8

16.2

9.5

8.6

9.0

Ratios 15 25 days

1 1.1

1 1.1

15371 "

1.1

1.0

25371 "

1.0

0.9

The question here arose whether this change in volume was in any way related to a shift in the long axis of the cell at the later ages. To answer this difficult question it was deemed desirable to compare the form of the ganglion cells obtained in the cross-section with that found in the radial section of the cochlea. In table 100 (chart 42) are given the values for the diameters of the cell bodies and their nuclei in the ganglion spirale in the cross-section. Below are given the respective ratios from 15 to 25, 15 to 371, and 25 to 371 days. Both cell body and nucleus increase in size up to twenty days and then diminish very slowly, as the age advances. These are similar to the relations found in the radial sections.

GROWTH OF THE INNER EAR OF ALBINO RAT

133

Looking at the diameters of the cell bodies and their nuclei in each turn (table 101), we do not find in the later age groups a regular increase in passing from the base toward the apex, as in the cells on the radial section. The differences are generally

TABLE 101

Diameter of the cell bodies and their nucki in the ganglion spirale according to the turns of the cochlea (cross section)

TURNS OV THE COCHLEA

AGE

BODT WEIGHT

I

II

ill

IV

Computed diameters ft

Cell body

Nucleus

Cell body

Nucleus

Cell body

Nucleus

Cell body

Nucleus

days 15

grams 20

15.0

8.7

14.7

8.8

14.9

8.9

14.9

9

20

27

16.7

9.7

17.2

10.0

17.5

10.1

18.1

10 6

25 100

39 95

16.9 17.2

10.0 10.0

17.2 16.9

9.9 9.6

17.6 16.7

9.8 9.6

17.3 16.8

10.0 9 6

150

169

17.0

9.9

16.6

9.3

16.6

9.4

16.4

9 1

371 Ratio 15-

220 371 days

16.2 1:1.1

9.6 1:1.1

16.2 1:1.1

9.1 1:1.0

16.0 1:1.1

8.7 1:1.0

16.3 1:1.1

9.0 1:1.0

20

15

10

AGE DAYS-

O

25

50

Chart 42 The average diameter of the largest cell bodies and of their nuclei of the nerve cells from the ganglion spirale, after 15 davs (cross-section) table 100.

Cell bodies. -.-.-.-.-. Nuclei.

134 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

far smaller than on the radial section. This result seems to have some connection with the position of the long axis of the ganglion cells in relation to the axis of the cochlea.

Comparing the diameters of the cell bodies and their nuclei in nearly corresponding places in the radial and cross-section, the long diameters of the cells are in each age group almost always larger in the radial than on the cross-section. Therefore the cells are somewhat ovoid. The short diameters, however, are at the same age sometimes longer, sometimes shorter on the radial than on the cross-sect on. This is probably due to the fact that in the upper turns the cells stand with their long diameter more nearly parallel to the axis of the modiolus, and therefore, on passing from the upper to the lower turn, the long axes of the cells become more inclined to the modiolus.

In order to show that the cell form is ovoid, I reconstructed the cells at 15, 100, and 365 days of age by the usual method, and obtained models which agreed in form with that determined by the microscope.

It appears, therefore, that while there is some difference in the diameters of these cells according to the plane of the section, neverthless, the change in volume after twenty days is similar in both cases, and so this change does not depend on the plane in which the sections were made.

On the nucleus-plasma relations of the cells in the ganglion spirale. The computed diameters of the cell bodies and their nuclei, measured on radial sections, are given in table 102 and the nucleus-plasma ratios have been entered in the last column. The ratio is at one day only 1:1.3 and increases rapidly and regularly till twenty days; after that period there are slight fluc- tuations. Generally speaking, the ratios increase with the ad- vancing age of the rat, but after twenty days only very slightly. Thus we see that the nucleus-plasma relation nearly reaches an equilibrium at twenty days, though the cells mature slowly even after that time.

When we consider this relation according to the turns of the cochlea, we find that this ratio increases in all the turns regularly and definitely till twenty days, after which there are some

GROWTH OF THE INNER EAR OF ALBINO RAT

fluctuations (table 103). Thus we see here also the same relation as before.

TABLE 102 Nucleus-plasma ratios of cells in the ganglion spirale (radial-vertical section)

AGE

BODY WEIOHT

BOOT LENGTH

COMPUTED DIAMETERS M

Cell body

Nucleus

N ucleus-plasma ratios

days

grams

mm.

1

5

48

10.5

7.9

1 : 1.3

3

8

56

11.5

8.0

2.0

6

11

63

12.9

8.4

2.6

9

10

58

13.6

8.5

3.1

12

13

60

13.8

8.5

3.3

15

13

75

14.9

8.7

4.0

20

29

95

18.1

10.2

4.6

25

36

104

17.7

10.1

4.4

50

59

125

17.5

10.0

4.4

100

112

159

16.9

9.5

4.6

150

183

190

16.7

9.2

5.0

257

137

175

16.8

9.6

4.4

366

181

191

16.9

9.4

4.8

546

255

213

16.9

9.4

4.8

TABLE 103

Nucleus-plasma ratios of cells in the ganglion spirale according to the turns of the cochlea. Based on table 96

AQB

BODY WEIOHT

TURNS Or THE COCHLEA

I

ii

in

IV

days

grama

1

5

1 :1.6

1 :1.5

1 :1.2

1 : 1.2

3

8

2.1

2.1

2.1

1.7

6

11

2.6

2.6

2.6

2.7

9

10

3.1

2.9

3.0

3.0

12

13

3.7

3.6

3.1

3.4

15

13

4.1

4.3

3.9

3.2

20

29

4.5

4.6

4.6

5.1

25

36

4.0

4.5

4.3

4.7

50

59

4.6

4.6

4.5

4.6

100

112

4.5

4.8

4.4

4.5

150

183

5.0

4.9

5.1

5.5

257

137

4.3

4.6

4.3

4.4

366

181

4.8

4.7

5.2

5.1

546

255

5.1

4.2

4.8

5.1

136

ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

In the nucleus-plasma ratio of the cells on the cross-section, as shown in table 104, the increase with age is very regular. As the diameters of the cell bodies and their nuclei decrease slowly after twenty days, this increase of the ratio means that the nuclei are diminishing relatively more rapidly than the cytoplasm.

Comparing these ratios from the radial and cross sections, we find that they agree (table 105) .

TABLE 104

Nucleus-plasma ratios of the cells in the ganglion spirale (cross-sections)

COMPUTED DIAMETERS M

BODY LENGTH

AGE

BODY WEIGHT

Cell body

Nucleus

Nucleus-plasma ratios

days

grams

mm.

15

20

84

15.0

8.8

1 4.0

20

27

93

17.4

10.1

4.1

25

39

114

17.3

9.9

4.3

100

95

152

16.9

9.7

4.5

150

169

192

16.7

9.4

4.6

371

220

206

16.2

9.0

4.8

TABLE 105

The nucleus-plasma ratios according to the plane of the section at two age periods

albino rat

AGE

NUCLEUS-PLASMA RATIO ON THE RADIAL SECTION

NUCLEUS-PLASMA RATIO ON THE CROSS SECTION

AGE

days 15

1 :4.0

1 :4.0

days 15

366

1 :4.8

1 :4.8

371

Discussion

According to the foregoing data, the maximum size of the cells in the ganglion spirale, at twenty days, is in cross-sections about 18.7 x 16.9 y. for the cell body and 10.3 x 10.0 [L for the nucleus. Both the long and short diameter of the cell body thus obtained is therefore a little less than that obtained in the radial section, while the diameters for the nu- cleus are the same.

In the literature we have not found any data for the Norway rat, but there are a few observations on the size of these cells in other mammals by Kolliker ('67) and von Ebner ('02).

Schwalbe ('87) and Alagna ('09) find these ganglion cells 25 to 30 JJL in diameter in the guniea-pig and cat.

Alexander ('99) has also reported measurements on a series of mammals, but as the size of such cells is greatly influenced by the method of preparation, and as our averages are based on the largest cells while those of other authors have been ob- tained in a different manner, it seems best not to report the other values in the literature, as they are sure to be misleading.

TABLE 106

Showing the changes with age in the diameters of the cells and the nticlei of the sjriral ganglion afnd the lamina pyrmidalis of the cerebral cortex, respectively

AGE '

CELL BODY IN THE OANQL. SPIRALS COMPUT- ED DIAM. M

CELL BODY IN THE LAMINA PYRAMID COM- PUTED DIAM.

NUCLEUS IN GANOL. SI-IK. COMP. DIAM.

NUCLEUS IN THE LAMINA PYRAM. COMP. DIAM.

AGE

days

days

1

10.5

11.4

7.9

9.4

1

20

18.1

18.7

10.2

15.7

20

546

16.9

17.0

9.4

13.8

730

Ratio be-

ratio

tween 1 and

1 : 1.7

1 :1.6

1 :1.3

1 :1.3

of Ito

20 days

20

days

Ratio be-

ratio

tween 1 and

1 : 1.6

1 : 1.5

1 :1.2

1 :1.2

of Ito

546 days

730

days

Considering the course of growth in these cells, we find it to be similar in both the spiral ganglion and the lamina pyramidalis of the cerebral cortex (rat) as reported by Sugita ('18). In the former the cells attain at twenty days of age, the time of wean- ing, their maximum size, and then diminish slowly with advancing age. The cells of the lamina pyramidalis also reach their full size at twenty days, and then diminish in the same way. There- fore, the course of the growth of both of these groups of nerve cells coincides. However, I do not know of other instances of the phenomenon. When tabulated, the relations here noted appear as in table 106.

The difference between them is only in the absolute values of the diameters of the cell bodies and especially of the nuclei,

138

the nuclei in the cells of the lamina pyramidalis being decidedly larger than in those of the spiral ganglion. The ratios of in- crease are, however, similar.

When we consider the increasing ratios of the diameters of the ganglion cells, we see a close similarity in the maximum values between the cells in the spiral and gasserian ganglion (Nittono, '20). Nevertheless while in the former the ratios from 1 to 20 and 1 to 366 days are in the cell bodies 1:1.7 and 1 : 1.6, respec- tively, in the latter the ratios for the corresponding intervals are 1: 1.43 and 1: 1.69, respectively (Nittono, '20, p. 235). In the nucleus also similar relations are to be seen in both ganglia.

As these ratios show, there is in the gasserian ganglion a definite increase in the diameters of cells and nuclei after 20 days of age; the time when the maximum is reached by the cells of the spiral ganglion. Thus the former continue to grow after growth in the latter has ceased. These results suggest that the neurons in the more specialized ganglia, like the spiral ganglion, may mature earlier than do those in the less specialized.

On the correlation between the growth of the hair cells of the papilla spiralis and of the nerve cells of the ganglion spirale. When we compare the growth changes in the hair cells with those in the ganglion cells, we find that the course of the development is similar. Both classes increase in volume from one to twenty days of age, then tend to diminish slowly the hair cells more slowly than the ganglion cells. In the ratios of increase, however, there are marked differences. Thus in table 67 (bottom of last column) the volume ratios from 1 to 20 and 20 to 546 days are 1 : 2.4 and 1 : 0.9, respectively in the hair cells, and in the ganglion cells, table 108, the ratios of the volumes in the fourth column work out for the corresponding ages as 1: 5.1 and 1: 0.8, re- spectively. In the case of the nuclei the growth changes are somewhat different. In the hair cells the nucleus grows in diameter more rapidly, and therefore reaches at nine days its maximum value and then diminishes at succeeding ages.

I have sought to determine whether there was any correlation in growth between either the entire cylindrical surface or the area of the cross-section of the hair cells, on the one hand and the volume

139

of the cells of the ganglion spirale on the other. The reason for making this comparison was the fact that Levi ('08), Busacca ('16), and Donaldson and Nagasaka ('18) have noted in the cells of the spinal ganglia of several mammals that the postnatal growth in volume was correlated with the increase in the area of the body surface, and recently Nittono ('20) has found in the rat a similar relation between the growth of the cells of thegasserian ganglion and the area of the skin of the head. On examining this problem, it is evident that the correlations thus far reported

TABLE 107

Comparison of ratios between the volumes of the cells of the ganglion spirale. nn<l ///

ratios of the area of the cylijidrical surface of the hair

cells of the organ of Corti on the maximum values

AOE

BOOT WEIGHT

VOLUME OP 1 III ClANllI.ION CELL, /'

RATIOS ON THE MAXIMUM VALUE

AKEA OF CYLINDRICAL SURFACE OF THE HAIR CF.LLH- M *

1ATIO8 ON THE MAXIMUM VALUE

days

gms.

I

5

606

3105

1 :5.12

395

723

1

1.83

3

8

796

3.90

463

1.56

6

11

1124

2.76

582

1.24

9

10

1317

2.36

648

1.12

12

13

1376

2.26

681

1.03

15

13

1732

1.79

729

0.99

20

29

3105

1.00

723

1.00

25

36

2903

1.07

691

1.05

50

59

2806

1.11

697

1.04

100

112

2527

1.23

678

1.07

150

183

2439

1.28

691

1.05

257

137

2483

1.25

689

1.05

366

181

2527

1.23

683

1.06

546

255

2527

1.23

699

1.03

apply to the postnatal growth period, and that we must consider that the functional relations of the skin are well established, even at the earliest age. The data with which we have worked in the case of the cochlea are presented in several tables (107 to 110).

In tables 107 and 108 are given the volumes of the cells of the ganglion spirale and the areas of the cylindrical surface of the hair cells. In table 107 the ratios are computed by dividing the maximum value by the values at each age, and in table 108 by dividing the values at each age by the initial value.

TABLE 108

Comparison of the ratios of the volume of the cells of the ganglion spirals with the

ratios of the area of the cylindrical surface of the hair cells of the organ of

Corti on the initial values

AGE

BOOT WEIGHT

VOLUME OF THE GANGLION

CELLS M *

RATIOS ON THE INITIAL VALUE

AREA OF THE CYLINDRICAL SURFACE OF THI HAIR CELLS M

RATIOS ON , THE INITIAL \ VALUE

days

grams

1

5

606 : 606

1

1.00

395

395

1

1.00

3

8

796

1.31

463

1.17

6

11

1124

1.85

582

1.47

9

10

1317

2.17

648

1.64

12

13

1376

2.27

681

1.72

15

13

1732

2.86

729

1.85

20

29

3105

5.12

723

1.83

25

36

2903

4.79

691

1.75

50

59

2806

4.63

697

1.76

100

112

2527

4.17

678

1.72

150

183

2439

4.02

691

1.75

257

137

2483

4.10

689

1.74

366

181

2527

4.17

683

1.73

546

255

2527

4.17

699

1.77

TABLE 109

Area of the cross-section of the inner and outer hair cells

WEIGHTED

DIAMETER OF

AVERAGE

DIAMETER OF

WEIGHTED

AGE

BODY

ONE INNER

DIAMETER OF

INNER AND

AREAS OF CROSS

WEIGHT

HAIR CELL

THREE OUTER

OUTER HAIR

SECTION OF

M

HAIR CELLS

CELLS

HAIR CELLS

M

M

M 2

days

grams

1

5

6.6

6.0

6.2

30

3

8

8.0

7.4

7.6

45

6

11

8.1

7.6

7.7

48

9

10

8.8

8.5

8.6

5S

12

13

8.5

8.3

8.4

55

15

13

8.4

7.7

7.9

50

20

29

8.8

8.2

8.4

55

25

36

8.8

8.1

8.3

55

50

59

8.8

8.2

8.4

55

100

112

8.6

8.1

8.2

53

150

183

8.5

8.3

8.4

55

257

137

8.5

8.3

8.4

55

366

181

8.8

8.4

8.5

58

546

255

8.6

8.2 | 8.3

55

GROWTH OF THE INNER EAR OF ALBINO RAT

141

I have calculated the cylindrical surface of the hair cells according to the formula for the lateral surface of a cylinder; therefore, this area equals 2 v r a (r = radius, a = height of the cylinder) . As the hair cells are more or less pointed at their lower end, the surface obtained by this formula has nearly the value of the total surface of the hair cells less that for the upper end disk.

As has been already shown, both classes of cells grow rapidly from birth to twenty days, and after that both tend to decrease slightly in volume. It is evident that during the growing period,

TABLE 110

Comparison of the ratios of the volume of the cells of the ganglion spirale with the

ratios of the areas of the cross-section of the inner and outer hair cells

of the organ of Corti

AOE

days

BODY WEIGHT

gms

VOLUME OF THE GANGLION CELLS M '

RATIOS ON THE INITIAL VALUE

AREA Or THE CROSS-SECTION OF THE HAIR CELLS

RATIOS ON THE INITIAL VALUE

1

5

606

606

1

1.00

30 :30

1

1.00

3

8

796

1.31

45

1.50

6

11

1124

1.85

48

1.60

9

10

1317

2.17

58

1 . 9

12

13

1376

2.27

55

1.83

15

13

1732

2.86

50

1.67

20

29

3105

5.12

55

1.83

25

36

2903

4.79

55

l s:;

50

59

2806

4.63

53

1.77

100

112

2527

4.17

53

1.77

150

183

2439

4.02

55

1.83

257

137

2483

4.10

55

1.83

366

181

2527

4.17

58

1.93

546

255

2527

4.17

55

1.83

from one day to the end of the record, the volumes of the ganglion cells increase more rapidly than do the cylindrical areas of the hair cells (table 108). If we seek a numerical expression of these relations, it seems best to start not with the values at birth, but with those at nine days of age when the cochlea is just beginning to function, and to extend the comparison only up to twenty days when both groups of cells have reached their maximum size. Thus at nine days (table 108) the volume of the ganglion cells is 1317 [A 3 , while at twenty days it is 3105 [A 3 , or as 1: 2.3, while the area of the cylindrical surfaces of the hair cells at the respective

142 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON

ages is 648 [x 3 and 723 [i 3 , or as 1 : 1.1, thus showing a rapid growth of the ganglion cell bodies accompanied by but slight enlargement of the hair cells.

It is evident from these ratios that the ganglion cells are increasing in volume more rapidly than the hair cells in area. It is possible that the nervus cochlearis innervates the other cells of the cochlea as well, but even if this is taken into con- sideration the general relations remain the same.

It follows from this that during the period between the earliest appearance of the functional response (nine days) and the attainment of the maximum size of the cells, the innervation of the hair cells is steadily improving, if we may infer such an improvement from the increase in the volume of the ganglion cells. After the close of this early growing period the relations are approximately fixed through the remainder of life. We do not find, therefore, in the cochlea any relation which corres- ponds to those found between the spinal ganglion cells or those of the gasserian ganglion and the associated areas of the skin during postnatal growth. This seems to indicate that in the cochlea growth is fixed or limited, while in the body as a whole it is more or less continuous, and the ganglion cells behave differently in the two cases.

In table 109 are shown the diameters of the inner and outer hair cells and their weighted diameters. In the last column is given the area of the cross-section of the hair cells.

The ratios of these areas on the initial area are shown in table 110 in comparison with the volumes of the ganglion cells on the initial volume, and indicate that from three days of age the values for the ganglion cells are increasing more rapidly than those for the area of the cross-section of the hair cells, and at twenty days the increase in the case of both elements has reached a maximum. Here, as in the case of the cylindrical surface, both elements show like phases of growth, but the increase in the volumes of the ganglion cells is much greater than the increase in the cylindrical area or cross-section of the hair cells.

As it may be desirable to use for comparison the measure- ments on the cells of the ganglion spirale as here reported, the

GROWTH OF THE INNER EAR OF ALBINO RAT

143

constants for the determinations based on 160 cells in each age group are given in . table 111 for the radial vertical sections and in table 112 for the cross-sections.

TABLE 111

A nalytical constants* giving the mean, standard deviation and coefficient of variability unth their respective probable errors for the diameters of the cells and their nuclei of the ganglion spirale in radial vertical section

AOK

days

FOR TOTAL NUMBER "K CELLS

Cell Nucleus

Mean

Standard deviation

Coefficient of variability

1

Cell

10.2 0.05

0.90 0.03

8.9 0.33

Nucleus

7.8 0.02

0.46 0.01

5.9 0.22

3

Cell

11.3 0.03

0.50 0.02

4.4 0.17

Nucleus

7.9 0.02

0.32 0.01

4.1 0.15

6

Cell

12.6 0.04

0.68 0.03

5.4 0.20

Nucleus

8.4 0.03

0.48 0.02

5.7 0.22

9

Cell

13.1 0.03

0.61 0.02

4.7 0.18

Nucleus

8.5 0.03

0.52 0.02

6.1 0.23

12

Cell

13.4 0.05

0.86 0.03

6.4 0.24

Nucleus

8.4 0.03

0.61 0.02

7.3 0.28

15

Cell

14.6 0.04

0.73 0.03

5.0 0.13

Nucleus

8.7 0.03

0.58 0.02

6.7 0.25

20

Cell

17.8 0.06

1.17 0.04

6.6 0.25

Nucleus

10.0 0.02

0.40 0.02

4.1 0.15

25

Cell

17.3 0.05

0.88 0.03

5.1 0.19

Nucleus

9.9 0.02

0.36 0.01

3.6 0.14

50

Cell

17.2 0.04

0.78 0.03

4.5 0.17

Nucleus

9.7 0.02

0.34 0.01

3.6 0.14

100

Cell

16.5 0.03

0.65 0.02

3.9 0.15

Nucleus

9.4 0.02

0.38 0.01

4.0 0.15

150

Cell

16.4 0.03

0.79 0.02

4.8 0.18

Nucleus

9.1 0.02

0.42 0.02

4.6 0.17

257

Cell

16.6 0.06

1.09 0.04

6.6 0.25

Nucleus

9.5 . 02

0.39 0.01

4.1 0.15

366

Cell

16.7 0.05

1.02 0.01

6.1 0.22

Nucleus

9.3 0.03

0.52 0.02

5.6 0.21

546

Cell

16.7 0.06

1 . 06 . 04

6.4 24

Nucleus

9.3 0.02

0.45 0.02

4.9 is

Conclusion

For the study of the growth of the nerve cells in the ganglion spirale fourteen age groups were taken and the data obtained from the 160 largest cells in each age group. Besides these, six age groups, representing six cochleas, were examined in cross-sections to determine the form of the ganglion cells and the relation of their long axes to the axis of the cochlea. Here also the ten largest cells in each of four, nearly corre- sponding turns, were measured. We obtained the following results :

1 . As thus prepared, the ganglion cells at birth have a maximum size of 11 x 10 [i in cell body and 8.2 x 7.6 [x in nucleus. At twenty days the diameters are the largest, 18.7 x 16.9 [x in cell body and 10.3 x 10.0 [x in nucleus.

TABLE 112

Analytical constants giving the mean, standard deviation and coefficient of vari- ability with their respective probable errors for the diameters of the cells and their nuclei of the ganglion spirale, in cross-section

AGE

CeU Nucleus

FOB TOTAL NUMBER OP CELLS

Mean

Standard deviation

Coefficient of variability

days 15

Cell

14.7 0.04

0.40 0.03

2.7 0.21

Nucleus

8.9 0.04

0.34 0.03

3.8 0.29

20

Cell

17.1 0.09

0.83 0.06

4.9 0.37

Nucleus

10.0 0.06

0.58 0.04

5.8 0.44

25

Cell

17.1 0.07

0.63 0.05

3.7 0.28

Nucleus

9.8 0.03

0.30 0.02

3.1 0.23

100

Cell

16.7 0.05

0.44 0.03

2.6 0.20

Nucleus

9.6 0.04

0.36 0.03

3.7 0.25

150

Cell

16.4 0.07

0.69 0.05

4.2 0.32

Nucleus

9 . 4 . 05

. 46 . 03

4.9 0.37

371

Cell

16.0 0.06

0.55 0.04

3.5 0.24

Nucleus

9.1 0.05

0.43 0.03

4.7 0.36

2. The ganglion cells grow relatively rapidly after birth and reach at twenty days of age their maximum size. After having passed the maximum at twenty days, they diminish in size very slowly, but the internal structure matures more and more with successive age.

3. The nuclei are relatively large at birth but increase more slowly than the cell bodies do; nevertheless, they follow the same course of development as the latter. This peculiar course in the growth of the ganglion cells is similar to that followed by the cells of the lamina pyramidalis of the cerebral cortex of the rat as found by Sugita ('18)

4. Within the cochlea the cell bodies and nuclei increase their diameters from the base toward the apex, except in the earlier stages.

5. There are no evident differences in the diameters of the cell bodies and the nuclei of the ganglion cells either according to sex or side.

6. Both the cell bodies and the nuclei are immature at birth, but differentiate rapidly, and even at six days the Nissl bodies are visible. The differentiation proceeds with advancing age.

7. The ganglion cells are bipolar and oval in shape. The direction of the long axis of the cells differs according to the turn of the cochlea and in the upper turn it runs almost parallel to the axis of the modiolus but inclines more and more to the horizontal position on passing to the base.

8. The nucleus-plasma ratios of the ganglion cells increase with age in both the radial and cross-sections.

9. The increase in the volume of the ganglion cells and the area of the cross-section of the hair cells is approximately sim- ilar during the first nine days of life, but after that the ganglion cells increase relatively very rapidly. These relations are very different from those found for the spinal ganglion cells by Don- aldson and Nagasaka ('18) and for the cells of the gasserian ganglion by Nittono ('20).

The nervus cochlearis innervates not only the hair cells, but all the elements of the cochlea, and this may have some in- fluence upon this relation. It is interesting to note that the rate of increase in the cylindrical surface of the hah* cells is similar to that in the area of the cross-sections of these same cells.