Book - Anatomical and physiological studies on the growth of the inner ear of the albino rat (1923): Difference between revisions
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5 (zona arcuata) and 10, which is the radial breadth of the zona | 5 (zona arcuata) and 10, which is the radial breadth of the zona | ||
pectinata of the membrana basilaris. | pectinata of the membrana basilaris. | ||
==III. On the Growth of the Largest Nerve Cells in the Ganglion Vestibulare== | ==III. On the Growth of the Largest Nerve Cells in the Ganglion Vestibulare== | ||
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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
Tokujiro Wada
Wistar Institute Of Anatomy And Biology
Contents
Introduction 5
Material 6
Technique 6
I. On the growth of the cochlea
A. On the growth of the radial distance between the two spiral ligaments 13
B. On the growth of the tympanic wall of the ductus cochlearis. . . 16
1. Membrana tectoria 28
2. Membrana basilaris 39
3. The radial distance between the habenula perforata and the inner corner of the inner pillar cell at base 47
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 48
5. The radial basal breadth of the outer pillar cell (including the outer pillar) 57
6. The radial distance between the habenula perforata and the outer border of the foot of the outer pillar cell 63
7. The greatest height of the greater epithelial ridge (dem grossen Epithelwulst Bottcher's s. Organon Kollikeri) resp. of the inner supporting cells 63
8. The radial distance between the labium vestibulare and the habenula perforata 68
9. The radial distance between the labium vestibulare and the inner edge of the head of the inner pillar cell 71
10. Vertical distance from the membrana basilaris to the summit of the pillar cells 75
11. The greatest height of the tunnel of Corti 77
12. The height of the papilla spiralis at the third series of the outer hair cells 77
13. The greatest height of Hensen's supporting cells 83
14. The angle subtended b> the extension of the surface of the lamina reticularis with the extended plane of the membrana basilaris 84
15. Lengths of the inner and outer pillar cells 85
16. Inner and outer hair cells 94
17. Deiter's cells 109
18. Summary and discussion 116
C. On the growth of the largest nerve cells in the ganglion spirale . 124
observations 124
Discussion 136
Conclusions . ... 143
II. Correlation between the inception of hearing and the growth of the cochlea
Observation 146
Discussion 152
Conclusions 155
III. On the growth of the largest nerve cells in the ganglion vestibulare
Material and technique 156
Observations 156
Discussion 165
Conclusions 168
Final summary 169
Literature cited . . . 171
Introduction
Since Alphonse Corti, in 1851, published his famous work on the cochlea of mammals, studies on this organ have been made by many authors and have produced fairly concordant results. Concerning the postnatal growth of the internal ear, however, systematic studies are lacking. Especially is there no investigation, so far as I know, on the growth of the nerve cells in the ganglion spiral, not even in the great work of Retzius. ('84).
It was the special object of these studies, therefore, to follow the growth of the cells forming the spiral ganglion from birth to maturity and to correlate the changes in them with the appearance of the functional responses and with the structural changes in the membranous cochlea. In the course of this investigation studies were made also on the cells of the ganglion vestibulare, in order to see whether these cells differed in their growth from the cells in the spiral ganglion. Both of these ganglia are situated in the course of nervus acusticus, but have, as is well known, entirely different functions.
Thus determinations have been made on the diameters of the cells of the ganglion spirale and of their nuclei at different ages; of the nucleus-plasma ratios and of then* growth in relation to those of other portions of the membranous cochlea. For the cells of the vestibular ganglion similar determinations were also made. Finally, these results have been compared with those obtained from the study of other craniospinal ganglia in the albino rat.
In presenting my results I shall begin with a description of the changes in the larger portions of the membranous cochlea and pass from these to the cell elements themselves, and then to the observations on the ganglion cells and to the correlation between hearing and the growth of the cochlea.
Material
For the present studies forty male and thirty female albino rats were used, representing every phase of postnatal growth and having approximately standard body weights. These were all from the colony of The Wistar Institute, and were sometimes from the same, and sometimes from different litters.
At first all these rats were tested for their ability to hear and their equilibrium, and it was ascertained that after about twelve days of age, or somewhat earlier, they responded positively to the test for hearing. Such examinations were deemed necessary, to make certain that the rats used were normal.
I have arranged the animals thus tested in fourteen groups according to age, each group having five individuals in it. Serial sections from all these cochleas were made by methods to be given later. Most of them were in the plane of the vertical axis of the cochlea, but some were at right angles to it.
From the former I selected four ears in each group for the study of the growth of the cochlea. For the study of the growth of the ganglion vestibulare, I have used for the most part the same specimens. For the study of the sections at right angles to the vertical axis of the cochlea, sections from one ear of each group were used.
Technique
In order to obtain good preparations of this delicate organ, the method of vital fixation (injection under anaesthesia) was used. The method employed, and which proved almost ideal, was that introduced by Metzner and Yoshii ('09), Siebenmann and Yoshii ('08) and somewhat improved by Sato ('17). After the animals had been tested to make sure that they were quite normal, the fixing solution was injected through the aorta under ether. The brain was then carefully removed, care being taken not to drag the trunk of the nervus acusticus, as noted by Nager ('05), and the bulla tympanica was opened to allow the further penetration of the fluid.
The bony labyrinth with its surrounding bones was then placed in the fixing solution for two weeks, the fluid being renewed every day.
The fixing solution which I used consists, according to Yoshii ('09), of
10 per cent formol 74 parts
M tiller's fluid 24 parts
Glacial acetic acid 2 parts
According to Tadokoro and Watanabe ('20), this solution is one of the best, ranking with that of Wittmaack ( '04, '06) and that of Nakamura ('14).
This injection method is sometimes difficult to apply to very young rats on account of the small size and the delicacy of the vessels. When injection failed in very young animals, then immediately the head was cut off and put directly in the fixing fluid. Owing to the incomplete calcification of the very young cochlea, the fixing solution enters rapidly and fixes the deepseated organs in good condition. Since the parts of the internal ear are not yet well developed in the very young rats, they do not suffer from this method of fixation as do the older cochleas.
Indeed, no differences are to be seen between the sections prepared by vital fixation and by decapitation in very young rats.
For decalcification I have employed the following solution during three days, renewing it every day.
Decalcifying fluid
5 per cent aqueous nitric acid 49 parts
10 per cent formol 49 parts
Glacial acetic acid 2 parts
After the specimens had been washed in running water for three days, they were passed through the alcohols from 50 to 97 per cent. For the imbedding I have used 'parlodion' with good results. Here it is to be mentioned that all the cochleas were treated in the same way, even unossified cochlea being passed through the decalcifying fluid, so that there should be absolutely no differences in treatment.
The next important matter is the determination of the plane
of the section. For the measurement of growth changes it was
necessary to obtain corresponding sections from the several
cochleas. In an organ like that of Corti, which changes in its
details from one end to the other, however, it is very difficult
to accomplish this, but I believe that I have overcome most of
the difficulties.
After much testing, I found that a section parallel to the under surface of os occipitale in the fronto-occipital direction runs nearly exactly parallel to the axis of the modiolus of the cochlea. In order to get the same direction from right to left, I have taken as the standard the transverse plane of the under surface of the os occipitale, controlling the direction of the section with a magnifying glass. Thus nearly the same radial direction and nearly corresponding places in the cochlea were obtained in the several series of sections. This makes possible a trustworthy comparison of the measurements and drawings.
The cross-section of the cochlea was gotten by making the plane of the cut transverse to the axis of the modiolus. To get the corresponding levels is difficult. At first I divided all the serial sections by 2^, which is the number of complete turns in the cochlea of the albino rat. Next, from the number of the slides representing each turn, I determined nearly the corresponding level in the cochlea according to age.
All the sections were 10;x in thickness. The sections were stained for the most part with haematoxylin and eosin, but sometimes by Heidenhain's iron haematoxylin or the iron haematoxylin and Van Gieson's stain. For the measurements, however, only the sections stained with haematoxylin and eosin were used.
For the examination of the larger parts of the cochlea and their relations, the sections were projected on a sheet of paper by the Leitz-Edinger projection apparatus, at a magnification of exactly a hundred diameters, and the outline of the image accurately traced. The remaining measurements of the ganglion cells and the smaller portions of the cochlea were made directly under the microscope. The measurements made on the tympanic wall of the cochlea are somewhat complicated, but by the aid of figures 1 and 2 they may be explained. In figure 1 lines 1-1, 1-1'. 2-2, 3-3 indicate, respectively, the height of the arch of Corti, of the tunnel of Corti, of the papilla spiralis (Huschke) at the third series of outer hair cells, and of Hensen's supporting cells, respectively, above the plane of the membrana basilaris.
Lines 4-4' which are the extensions of the surface of the lamina reticularis and of the membrana basilaris, subtend the angle 8.
To get the exact measurements of the radial breadth of the membrana tectoria is very difficult, if not impossible, because it is sinuous in its course; moreover, it differs in thickness from point to point. Therefore, it has been variously described by different authors. Intra vitam fixation tends to prevent distortion. We divide the membrana tectoria, figure 1, into two portions, the first or inner (7-7'-9-9') and the second or outer (5-5 '-7-7') or outer zones of Retzius; each of these is again divided in two at 6-6' and 8-8', as shown in figure 1.
I have measured the radial distance of each portion and added all four together. This total approximates the natural radial breadth of this membrane, and since the sections have all been prepared in the same way and examined by the same method, the relations during growth can be followed.
In figure 2, 1-1 and 2-2, mark the length of the inner and outer pillar cells, respectively, from base to the point, which is situated just under their junction. It is to be noted here that the term ' pillar cell ' here applies to the pillars in the strict sense and does not include the associated cells.
Distances 3 and 7 in figure 2 show the basal breadth of the inner and outer pillars, respectively. The former is identical with the distance between the habenula perforata and the outer corner of the inner pillar after the inner corner of the pillar has reached the habenula perforata, but there is some difference between the two distances in very young rats. Distance 4 is that between the habenula perforata and the inner corner of the outer pillar; distance 5 is that between the habenula perforata and the outer corner of the outer pillar. The latter represents at the same time the radial breadth of the zona arcuata of the membrana basilaris.
Fig. 1 Showing the localities for the measurement of each part of the tympanic wall of ductus cochlearis in the albino rat, 100 days old radial vertical
section. 1-1, height from the basal plane to the surface of pillar cells; 1-1',
greatest height of the tunnel of Corti; 2-2, height of papilla spiralis at the third
series of the outer hair cells; 3-3, height of Hensen's supporting cells; 4~4', 4
indicates the extension of the membrana basilaris and 4' the extension of the
lamina reticularis. The two lines subtend the angle 0. The radial breadth
of the membrana tectoria is taken as the sum of the four segments between the
lines 5-5' and 9-9'.
Fig. 2 Showing the method of measurement for several parts of the tympanic wall of the ductus cochlearis in the albino rat, 100 days old. 1-1, length of inner pillar cell without head; 2-2, length of outer pillar cell without head Distance 3 shows radial distance between habenula perforata and the outer corner of inner pillar at base after twelve days of age this equals the radial basal breadth of inner pillar. Distance 4, radial distance between habenula perforata and the inner corner of outer pillar at base. Distance 5, radial breadth of the zona arcuata (Deiters') of membrana basilaris, and at the same time it indicates radial distance between habenula perforata and the outer corner of outer pillar at base. Distance 6, radial distance between the outer corner of inner pillar and the inner corner of outer pillar at base. Distance 7, radial basal breadth of outer pillar. Distance 8, radial distance between the habenula perforata and outer corner of inner pillar cell at base. Distance 9, radial basal breadth of the outer pillar cell. Distance 10, radial breadth of zona pectinata of the membrana basilaris. Distance 11, radial breadth of entire membrana basilaris.
Fig. 3 Showing the general outline of the cochlea in the radial vertical section albino rat, 100 days of age.
Abbreviations
Line 1, 1, distance between two basal L.L.S., limbus laminae spiralis
spiral ligaments L.S., ligamentum spirale
Line 2, 2, distance between two apical L.S.O., lamina spiralis ossea
spiral ligaments M.T., membrana tectoria
7, first turn N.C., nervus cochlearis
II, second turn O., bone
///, third turn P.S., papilla spiralis
IV, fourth turn S., stria vascularis
D.C., ductus cochlearis S.T., scala tympani
G.S., ganglion spirale S.V., scala vestibuli G.V., ganglion vestibulare
Distance 6 is that between the outer corner of the inner pillar
and the inner corner of the outer pillar. Distance 8 is that
between the habenula perforata and the outer corner of the inner
pillar cell. Distance 9 shows the radial basal breadth of the
outer pillar cell plus the outer pillar. Distance 11 shows the
radial breadth of the membrane basilaris comprising distance
5 (zona arcuata) and 10, which is the radial breadth of the zona
pectinata of the membrana basilaris.
III. On the Growth of the Largest Nerve Cells in the Ganglion Vestibulare
Material and technique
The material used for the present study was in a great part the same that was employed for the studies reported in chapter 1, with the addition of some new specimens as shown in table 114 and table 94. In the slides obtained in the radial vertical section we see the vestibular ganglion cells situated in a single group at the radix of the cochlea (Fig. 3 G. V.). As four ears were used in each age group, four cell groups were examined at each age. Besides these fourteen age groups, six rats used for cross-sections, in chapter 1, were also included.
The measurements were made in the same way and under the same conditions as those described earlier for the cells of the spiral ganglion. Since the ganglion vestibulare consists of two parts, the ganglion vestibulare superius and inferius, the ten largest cells were taken from each part and the results averaged.
Observations
By way of introduction I wish to say a word about equilibration in the young rat. The young just born crawl over on each other and seem to attempt to find the mothers nipples. They turn the head to and fro and roll over on the flanks, belly, or back. While resting they take their normal position or lie on the side. When turned on their backs they endeavor to regain the normal
GROWTH OF THE INNER EAR OF ALBINO RAT
157
position. The fore legs are of more use than the hind in making readjustments. The tails hang down between the hind legs.
TABLE 114
Data on rats used for the study of the cells of the ganglion vestibulare (radial section).
See also table 94
AOB
BOOT
WEIGHT
BODY
LENGTH
BEX
BIDE
AUDITOHT
RESPONSE
days
grams
mm.
1
5
44
9
R.
4
44
9
R.
5
48
d 1
R. L.
3
9
60
<?
R. L.
8
56
9
R. L.
6
10
64
a
R.
10
64
9
R. L.
11
62
(7
R.
9
11
67
<?
R. L.
+
9
58
9
R.
10
57
tf
R.
12
13
70
d 1
R. L.
+
12
68
9
R.
+
15
72
c?
R.
+
15
13
74
d"
R. L.
+
14
75
9
R. L.
+
20
30
.96
d 1
R. L.
+
28
94
c?
R. L.
+
25
34
101
9
R. L.
+
34
100
d 1
R. L.
+
50
58
121
9
R. L.
+
43
104
(f
R. L.
+
100
146
176
c?
L.
+
103
154
9
L.
+
101
152
9
R. L.
+
150
154
184
9
R. L.
+
189
191
c?
R.
+
199
192
d 1
R.
+
260
137
162
9
R.
+
140
171
9
R. L.
+
134
178
9
R.
' +
367
205
202
rf
L.
+
170
182
9
L.
+
179
196
9
R. L.
+
546
282
222
d 1
R. L.
+
227
204
d 1
R. L.
+
At three days they move and crawl very actively. They tend to assume the normal position. When rolled over on the back or side they succeed in regaining the normal position in
158
ANATOMICAL AND PHYSIOLOGICAL STUDIES ON
a few seconds. When six days old the rats have fairly well coordinated movements. They use their fore and hind legs effectively and in the same way. When the mother 's body touches them they respond quickly by searching for the nipples.
At nine days they move much more quickly and the movements are well coordinated. .Though the eyes are still closed, they
TABLE 115
Diameters of the cells and their nuclei in the ganglion vestibulare in radial vertical section
(Chart 43)
AGE
BODY
WEIGHT
DIAMETERS IN M
CELL BODY
NUCLEUS
Long
Short
Computed
Long
Short
Computed
days
grams
1
5
21.2
19.5
20.3
12.4
11.1
11.7
3
9
23.7
22.2
22.9
12.5
11.6
12.0
6
11
24.0
22.1
23.0
12.3
11.9
11.9
9
10
24.8
23.0
23.9
12.5
11.6
12.0
12
13
24.9
23.0
23.9
12.5
11.7
12.1
15
13
24.8
23.0
23.9
12.5
11.6
12.0
20
27
25.0
23.3
24.1
12.3
11.6
11.9
25
34
25.2
23.6
24.4
12.5
11.8
12.1
50
50
25.6
23.6
24.5
12.5
11.6
12.0
100
112
25.5
23.9
24.7
12.8
11.9
12.3
150
174
25.4
23.5
24.4
12.8
11.6
12.2
260
138
25.8
23.4
24.6
12.4
11.7
12.0
367
184
26.2
24.9
25.5
12.9
11.8
12.3
546
255
26.5
24.2
25.3
12.8
11.8
12.2
Ratios 1
-367 days
1 1.3
1:1.1
1546 "
1.2
- 1.0
15367 "
1.1
- 1.0
crawl toward the object sought. When turned over on the back they regain the normal position immediately. While resting they lie on their bellies with all the legs spread well apart.
Twelve-day-old rats, though the eyes are still closed, go to and fro actively with good coordination, but are somewhat slower than the adults. The body loses its fetal red color through the development of the first hairs. After this period the rats do not differ greatly from the adult in their general behavior.
GROWTH OF THE INNER EAR OF ALBINO RAT
159
The growth changes in the ganglion cells of the ganglion vestibulare. In table 115 (chart 43) are given the values for the diameters of the cell bodies and their nuclei in the largest cells of the ganglion vestibulare. At the bottom of the last column for the cell body and for the nucleus, respectively, are recorded the ratios at 1 to 367, 1 to 546, and 15 to 367 days. The last ratio was taken
25
a
20 15 10
- GEDAYSH
25
50
5O 1OO 2OO 30O 4OO 5OO
Chart 43 The diameter of the largest cell bodies and of the nuclei from the ganglion vestibulare. table 115.
Cell bodies. -.-.-.-.-. Nuclei.
to facilitate a comparison with the data in table 118 which begin at 15 days.
Looking at the ratios of the cell bodies and of their nuclei from 1 to 546 days, it appears that the ganglion cells increase 1.2 in diameter, while their nuclei have only a very slight increase, and therefore the ratio is 1 : 1.0. This increase in the cell bodies is continuous from birth to old age, but after fifteen days is very slow. In the nucleus we see a slight increase at the earlier
160 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON
ages, after which the values are nearly constant. This means that after birth the size of the cell bodies and their nuclei does not increase so much as do those of the spiral ganglion cells, or, expressed in another way, the cells in the vestibular ganglion have developed earlier than those of the spiral ganglia and at birth have already attained nearly their full size.
On the comparison of the diameter of the cell bodies and their nuclei in the nerve cells of ihe ganglion vestibulare according to sex. For this purpose twelve age groups of albino rats were used. In seven cases we have two cochlea in each group in the same sex, in which the average value is recorded. In table 116 are entered the values for these diameters and at the foot of the table the data are analysed. They reveal no evidence of a significant difference in the diameters according to sex.
On the comparison of the diameters in the cell bodies and nuclei of the nerve cells in the ganglion ves ibulare according to side. For the present study fourteen age groups were employed. As indicated in table 117, the data in five instances are based on the average of two cochleas of the same side. Table 117 enables us to make the comparison of the diameters of the cell bodies and their nuclei on both sides, and the analysis of the data given at the bottom of the table shows that there is no difference in these characters according to side.
On the morphological changes in the cells of the vestibular ganglion. Figure 14 illustrates semi-diagrammatically the ganglion cells in the vestibular ganglion of the albino at birth, 20 and 367 days of age. These figures, as in the ganglion spirale, have been magnified 1000 times and the absolute values of the diameters are given in table 115.
As seen in figure 14, both the cell body and the nucleus are at birth already well developed and more precocious in their development than the cells in any of the other cerebrospinal ganglia thus far examined. The cytoplasm is relatively abundant and the Nissl bodies are present, though both of these characters become more marked later.
The nucleus is also large, the chromatin somewhat differentiated and the so-called 'Kernfaden' often occur. Generally speaking,
I Day
20 Days
14
366 Days
Fig. 14 Showing setrii-diagrammatically the size and the morphological changes in the ganglion cells in the ganglion vestibulare of the albino rat at the age of 1, 20 and 366 days. All cell figures have been magnified 1000 diameters.
GROWTH OF THE INNER EAR OF ALBINO RAT
161
therefore, the cells have the characteristics of the mature elements though they stain less deeply than in the adult. At twenty days of age the cell body is enlarged and fully mature. The Nissl
TABLE 116
Comparison of the diameters of the cells and their nuclei in the ganglion vestibidare
according to sex
AGE
BODY
WEIGHT
NUMBER OF
RATS
8EX
COMPUTED DIAMETERS
Cell body
Nucleus
days
grams
1
6
2
f
20.8
11.9
9
19.9
11.5
3
9
2
tf
21.7
11.8
8
2
9
23.8
12.2
6
11
2
tf
22.7
11.9
10
2
9
23.1
12.1
9
11
1
d*
23.8
12.5
9
1
9
23.8
12.1
12
15
1
cf
24.4
12.2
12
1
9
23.1
11.9
15
13
2
cf
24.3
12.2
13
2
9
23.4
11.9
20
30
1
cf
24.7
11.9
19
1
9
24.6
12.6
25
34
2
d"
24.4
11.9
34
2
9
24.4
12.4
50
43
2
cT
26.1
12.4
58
2
9
22.6
11.4
100
146
1
<?
26.3
12.8
103
1
9
23.4
12.6
150
194
2
rf 1
24.4
12.5
154
2
9
24.4
12.0
365
205
1
<f
24.2
11.7
170
1
9
24.6
12.1
Average for male
24.0
12.1
Average for female
23.4
12.1
Males larger
6
7
Females larger
3
5
Males and females equal
3
bodies are more differentiated and the nucleus is mature, though
it shows only a slight increase in size.
At 367 days the histological structures appear much as at twenty days, but the diameters of both the cell body and the nucleus have very slightly increased. This is in contrast to the change which occurs in the cells of the spiral ganglion.
162
ANATOMICAL AND PHYSIOLOGICAL STUDIES ON
In order to study the form of the cells of the ganglion vestibulare the measurements also were made on the cross-sections. Table
TABLE 117
Comparison of the diameters of the cells and their nuclei in the ganglion vestibulare according to side
AGE
BODY
WEIGHT
NUMBER
OF RATS
SIDE
COMPUTED DIAMETERS
Cell body
Nucleus
days
grams
1
4
1
R.
20.1
12.0
5
1
L.
22.0
12.5
3
9
2
R.
23.0
11.8
L.
22.6
12.3
6
10
1
R.
23.2
12.1
L.
23.5
12.0
9
11
1
R.
25.1
12.3
L.
23.8
12.5
12
15
1
R.
24.4
12.2
13
1
L.
25.1
12.5
15
13
2
R.
24.2
12.2
L.
23.6
11.9
20
30
1
R.
24.7
11.9
L.
23.5
11.4
25
34
2
R.
23.9
12.1
L.
24.9
12.2
50
50
2
R.
23.1
11.6
L.
25.6
12.3
100
101
1
R.
25.0
12.0
L.
24.8
11.7
150
199
1
R.
25.1
12.8
154
1
L.
25.4
12.5
263
140
1
R.
26.5
12.3
L.
25.1
12.4
368
179
1
R.
27.2
12.6
L.
26.2
13.0
546
255
2
R.
26.0
12.4
L.
24.6
12.0
Average right side
24.4
12.2
Average left side
24.3
12.2
Right larger
8
6
Left larger
6
8
118 (chart 44) shows the results. Looking at the ratios of 15 to 371 days, we see the same rate of increase in the cell bodies and the nuclei as that in the radial section; i.e., in the cell bodies 1 : 1.1 and in the nuclei 1 : 1.0. Comparing the diameters at each
GROWTH OF THE INNER EAR OF ALBINO RAT
163
TABLE 118
Diameters of the cell bodies and their nuclei in the ganglion vestibulare, on crosssection (chart 44)
DIAMETERS M
AOK
BOOT
WEIGHT
CELL BODY
NUCLEUS
Long
Short
Computed
Long
Short
Computed
days
grams
15
20
25.1
22.8
23.9
12.4
11.6
12.0
20
27
25.2
23.4
24.3
12.5
11.7
12.1
25
39
25.2
24.0
24.6
12.3
12.0
12.1
100
95
26.6
24.7
25.6
12.8
11.8
12.3
150
169
26.7
24.7
25.7
13.0
11.7
12.3
371
220
26.8
25.3
26.0
12.8
11.8
12.3
Ratio 15-371 days 1:1.1
1 :1.0
25
20
15
10
25
50
50 10O 20O 300 40O 5OO
Chart 44 The diameters of the cell bodies and of their nuclei from the ganglion vestibulare, after fifteen days (cross-section), table 118. Cell bodies. -.-.-.-.-. Nuclei.
164
ANATOMICAL AND PHYSIOLOGICAL STUDIES ON
age in both the radial and cross-sections, they are almost the same, with a slight tendency for the cells in the cross-section to give higher values, which suggests that the long axes of these cells tend to lie in the plane of the section.
On the nucleus-plasma relations of the ganglion cells in the ganlion vestibulare. In table 119 are entered the computed diameters of the cell bodies and their nuclei in the radial section, and in the last column the ratios of the volume of the nucleus to that of the cytoplasm obtained by the method previously given. As
TABLE 119
Nucleus-plasma ratios of the cells in the. ganglion vestibulare radial vertical section
COMPUTED DIAMETERS M
AGE
BODY WEIGHT
Cell body
Nucleus
Nucleus-plasma
ratios
days
1
grams
5
20.3
11.7
1 :4.2
3
9
22.9
12.0
- 5.9
6
11
23.0
11.9
- 6.2
9
10
23.9
12.0
- 6.9
12
13
23.9
12.1
- 6.7
15
13
23.9
12.0
- 6.9
20
27
24.1
11.9
- 7.3
25
34
24.4
12.1
- 7.2
50
50
24.5
12.0
- 7.5
100
112
24.7
12.3
- 7.1
150
174
24.4
12.2
- 7.0
260
138
24.6
12.0
- 7.6
367
184
25.5
12.3
- 7.9
546
255
25.3
12.2
- 7.9
seen, the ratio is at birth relatively large, 1 : 4.2, and this increases with age, in the earlier stages considerably, but in the later, less rapidly. In the oldest age group it is largest, 1: 7.9.
On the cross-section the nucleus-plasma ratio is also progressive and the increase is very regular (table 120). Comparing the ratios in the radial with those in the cross-sections, they are found to be nearly the same at fifteen twenty and twenty-five days, but at the later ages those in the cross-sections are somewhat larger than in the radial. It is difficult to determine whether the ratios on the cross-section are really larger or whether the
GROWTH OF THE INNER EAR OF ALBINO RAT
105
result depends on the fact that the number of the cells here measured is only one-fourth of that measured in the radial section, and hence fewer cells of smaller size were included. At any rate, these ganglion cells in both the radial and crosssections of the cochlea appear to grow at about the same rate. The statistical constants for these cells and their nuclei are given in tables 121 and 122.
Discussion
The nerve cells in the ganglion vestibulare are, as seen from the above description, already well developed at birth both in size and histological structure. After that time they grow con TABLE 120
Nucleus-plasma ratios of cells of the ganglion vestibulare, in cross-section
DIAMETERS COMPUTED M
BOOT
AGE
WEIGHT
Cell body
Nucleus
Nucleus-plasma
ratios
days
grams
15
20
23.9
12.0
1 :6.9
20
27
24.3
12.1
- 7.1
25
39
24. ti
12.1
- 7.4
100
95
25.6
12.3
- 8.0
150
169
25.7
12.3
- 8.1
371
220
26.0
12.3
- 8.4
tinuously but slowly so long as followed. The increase from 1 to 546 days in the ratios of the diameters is in the cell body 1: 1.3, in the nucleus 1: 1.1, and is therefore very small. In the cerebrospinal ganglion cells and in the cells of the cerebral cortex, studied in the albino rat, there is no case which shows such a small rate of increase between birth and maturity. The following table 123 shows the ratios of increase which have been found.
It is to be noted that for the cells of the seventh spinal ganglion and the spinal cord, the ratios were taken from 17 to 360 days. If we had the ratios from 1 to 360 days, they would be without question much larger.
There are a few measurements on the size of the ganglion cells in the vestibular ganglion of various animals in the liter
166
ANATOMICAL AND PHYSIOLOGICAL STUDIES ON
ature. Schwalbe ('87) and Alexander ('99) report measurements on these cells in several animals, but for the reasons already given when considering the diameters of the cells in the ganglion spirale, the values obtained by the authors are not repeated here.
TABLE 121
Giving the mean, standard deviation and coefficient of variability, with their respective probable errors, for the diameters of the cells in the ganglion vestibulare, in radial-vertical section
AGE
CELL
NUCLEUS
MEAN
STANDARD
DEVIATION
COEFFICIENT OF
VARIABILITY
days
1
Cell
20.1 0.16
1.46 0.11
7.3 0.55
Nucleus
11.7 0.11
0.99 0.07
8.5 0.64
3
Cell
22.6 0.14
1.33 0.10
5.9 0.44
Nucleus
11.9 0.07
0.63 0.05
5.3 0.40
6
Cell
22.8 0.13
1.23 0.09
5.4 0.41
Nucleus
11.9 0.05
0.43 0.03
3.6 0.27
9
Cell
23.6 0.16
1.48 0.11
6.3 0.48
Nucleus
12.0 0.0<9
0.82 0.06
6.8 0.52
12
Cell
23.6 0.14
1.28 0.10
5.4 0.41
Nucleus
12.0 0.06
. 59 . 04
4.9 0.37
15
Cell
23.6 0.13
1.21 0.09
5.1 0.39
Nucleus
12.1 0.06
0.60 0.05
5.0 0.38
20
Cell
23.9 0.16
1.54 0.11
6.5 0.49
Nucleus
11.9 0.10
0.90 0.07
7.6 0.55
25
Cell
24.2 0.16
1.48 0.11
6.1 0.46
Nucleus
12.1 0.08
0.74 0.06
6.1 0.46
50
Cell
24.1 0.30
2.80 0.21
11.6 0.88
Nucleus
11.8 0.09
0.86 0.06
7.3 0.55
100
Cell
24.3 0.20
1.86 0.14
7 . 7 . 58
Nucleus
12.2 0.09
0.86 0.06
7.0 0.53
150
Cell
24.1 0.18
1.70 0.13
7.1 0.53
Nucleus
12.2 0.09
0.83 0.06
6.8 0.52
260
Cell
24.3 0.26
2.45 0.18
10.1 0.76
Nucleus
11.9 0.07
0.67 0.05
5.6 0.42
367
Cell
25.2 0.22
2.07 0.16
8.2 0.62
Nucleus
12.3 0.09
0.88 0.07
7.2 0.54
546
Cell
25.0 0.19
1.80 0.14
7.2 0.54
Nucleus
12.1 0.09
0.81 0.06
6.7 0.50
On the differences between the growth of the cells in the ganglion spirale and ganglion vestibulare. The foregoing discussion has made plain that the vestibular ganglion cells grow not only in size, but also in histological structure very much before birth, while after birth they grow slowly though continuously. On the other hand, the spiral ganglion cells are relatively immature at
GROWTH OF THE INNER EAR OF ALBINO RAT
167
birth, but in the earlier stages after birth grow very rapidly, reach at twenty days their maximum size, and then diminish slowly. This great difference in the course of growth is probably related to the maturity of the functions of the animal.
TABLE 122
Giving the mean, standard deviation and coefficient of variability with their respective probable errors for the diameters of the cells in the ganglion vestibulare on cross-section
AGE
days
CELL
NUCLEUS
MEAN
STANDARD
DEVIATION
COEFFICIENT OF
VARIABILITY
15
Cell
23.8 0.21
1.00 0.15
4.2 0.58
Nucleus
12.0 0.12
0.55 0.08
4.6 0.69
20
Cell
23.9 0.20
0.92 0.14
3.9 0.58
Nucleus
12.1 0.06
0.30 0.05
2.5 0.37
25
Cell
24.4 0.20
0.94 0.14
3.9 0.58
Nucleus
12.1 0.03
0.16 0.02
1.3 0.20
100
Cell
25.4 0.32
1.51 0.23
5.9 0.90
Nucleus
12.3 0.15
0.72 0.11
5.9 0.88
150
Cell
25.6 0.20
0.94 0.14
3.7 0.55
Nucleus
12.4 0.09
0.42 0.06
3.4 0.51
371
Cell
25.9 0.41
1.91 0.29
7.4 1.11
Nucleus
12.3 0.06
0.26 0.04
2.1 0.32
TABLE 123 Ratios of diameters between the ages given.
CEREBRAL CORTEX
DONALDSON AND
(SUGITA, '18)
NAOABAKA. '18
CELL
GROUP
LAMINA
LAMINA
OA88ERIAN
SPIRAL
VESTIBULAR
7TH
EFFERENT
PYHA
GANO
GANGLION
GANGLION
GANGLION
SPINAL
SPINAL
MIDIS
LIONARIS
NITTONO
WADA
WADA
GANGLION
CORD
C20)
CELLS
Age
days
1-730
1-730
1-330
1-546
1-546
17-360
17-360
Cell
body
1 :1.6
1 : 1.6
1 : 1.69
1 : 1.6
1 :1.2
1 :1.3
1 :1.2
Nucleus
- 1.5
- 1.5
- 1.20
- 1.2
- 1.0
- 1.2
- 1.2
As a consequence, in the nucleus-plasma ratio there is also a large difference between the cells in the two ganglia. Table 124 shows this.
The ratio at birth in the ganglion vestibulare is large as compared with that in the ganglion spirale, but the increase in this ratio
168 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON
at 546 days is relatively slight as compared with what takes place in the cells of the ganglion spirale. It appears, therefore, that the cells in the vestibular ganglion are at birth in a more mature condition.
As to the correlation between the development of the ganglion cells and the equilibrium function, we have noted that the albino rats, even just after birth, show some sense of equilibrium, though the movements are lacking in coordination. With advancing age the balance of the body is held much better and all the movements gradually become coordinated. The histological structure and the size of the cells at birth suggest that they are functional at that time, and the later increase in the volume and maturity of the cells is accompanied by a corresponding
TABLE 124
GANGLION VESTIBULARE
GANGLION
SPIRALE
Nucleus-plasma ratio at one day
Nucleus-plasma ratio at 546 days
1 :4.8
- 7.9
1 : 1.3
- 4.2
increase in the functional development. When the tactile sense is well developed and the eyes open equilibrium is almost perfected. It is a well-known fact that these two senses have very intimate relations to the maintenance of equilibrium. In this case, as we might expect, the early development of a function is accompanied by an early maturing of the neural mechanism on which it depends.
Conclusions (for the ganglion vestibulare)
1. The measurements were taken on the largest nerve cells of the ganglion vestibulare in the radial section of the cochlea, and the developmental changes during portnatal growth studied in fourteen age groups, comprising four ears in each group. Further, in six age groups the cell size was determined in crosssections. The results have been given n tables 115 and 118 and charts 43 and 44.
GROWTH OF THE INNER EAR OF ALBINO RAT 169
2. The computed diameter at birth is 20.3 [x for the cell body and 11.7 ^ for the nucleus, and at 546 days, 25.3 and 12.2 n, respectively. Therefore the cells at birth are comparatively large and increase in size very slowly, but the increase is continuous.
3. The increase in the ratio of the cell body is as 1 : 1.3, of the nucleus as 1 : 1.1. We have between the same age limits no such small rate of increase in any other cerebrospinal ganglion studied in the albino rat. This small ratio indicates that the cells in the vestibular ganglion are well developed at birth.
4. We find no appreciable difference in the diameters of the cell bodies or the nuclei according either to sex or side.
5. Morphologically, the cells at birth are well differentiated. The form of the cells is ovoid.
6. The nucleus-plasma ratios are large at birth and increase regularly with age.
7. Comparing the development of the function of equilibrium with the growth of the cells, we see that these are correlated.
Final summary
This study is concerned with the age changes in the organ of Corti and the associated structures. The changes in the largest nerve cells which constitute the spiral ganglion and the vestibular ganglion, respectively, have also been followed from birth to maturity. On pages 116 to 124 are given the summary and discussion of the observations on the growth of the tympanic wall of the ductus cochlearis.
The conclusions reached from the study of the largest nerve cells in the ganglion spirale appear on pages 143 to 145. On pages 155 and 156 are presented the results of the study on the correlation between the response to sound and to the conditions of the cochlea.
Finally, the observations on the growth of the largest cells in the ganglion vestibu'are are summarized on pages 168 and 169.
It is not necessary to again state in detail the conclusions reached in the various parts of this study.
At the same time, if we endeavor to obtain a very general picture of the events and changes thus described, this may be sketched as follows:
170 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON
Within the membranous cochlea there occurs a wave of growth passing from the axis to the periphery as shown in figures 4 to 13. The crest or highest point of the tissue mass appears at birth near the axis, in the greater epithelial ridge, and then progressively shifts toward the periphery, so that at maturity it is in the region of the Hensen cells. With advancing age the hair cells come to lie more and more under the tectorial membrane and the pillar cells seem to shift toward the axis.
At from 9 to 12 days the tunnel of Corti appears and the rat can hear.
All of these changes occur first in the basal turn and progress toward the apex. The mature relations are established at about twenty days. There are thus two waves of change in the membranous cochlea, from the axis to the periphery and the other from the base to the apex. The rat can usually hear at twelve days of age or about three days before the eyes open.
The largest cells in the ganglion spirale are very immature at birth, reach their maximum at twenty days, and after that diminish in size, slightly but steadily. The rat hears, therefore, before these cells have reached their full size.
The largest cells in the vestibular ganglion are precocious and remarkably developed, even at birth. They cease their rapid growth at about fifteen days of age, but increase very slightly though steadily throughout life.
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