Paper - The lateral wall of the cavum nasi in man, with especial reference to the various developmental stages
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Schaeffer JP. The lateral wall of the cavum nasi in man, with especial reference to the various developmental stages. (1910) J Morphol. 21: 613-708.
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The Lateral Wall of the Cavum Nasi in Man, with Especial Reference to the Various Developmental Stages
Jacob Parsons Schaeffer
Cornell University Medical College, Ithaca; N.Y. (1910)
A survey of the literature on the lateral wall of the cavum nasi indicates that commendable researches have been carried out by different investigators. Although much careful work has been done, conﬂicting opinions are held on some points of the development and the gross anatomy of this portion of the olfactory organ. The idea of an unvarying typical form in the gross anatomy of the structures and relations in this region of the nose seems too much in evidence in some of the general textbooks of anatomy. In fact the exceptions in some instances to the descriptions given are so numerous that the exception is described rather than the average condition. This is especially true in the manner of communication of the nasofrontal duct ‘with the middle nasal meatus. The ostium maxillare accessorium—a very common aperture indeed—does not receive the recognition it should have. According to my series of specimens, 62.5 per cent of ethmoidal regions possess in the adult three conchae. Books generally describe and picture two ethmoidal conchae as the typical number, and apparently Would have us think that three ethmoidal conchae are rather exceptional.
In order to determine whether the embryology would account for the varied adult conditions one meets, I undertook the study of the various developmental stages in the formation of the complex lateral nasal wall. It was deemed essential that the embryological stages in the formation of the nasal cavity be considered before taking up for detailed study its lateral wall. The paper will, therefore, include: (1) a brief description of the developmental stages of the nasal fossae; (2) the detailed embryology of the lateral walls of the nasal fossae ; (3) the gross anatomy of the lateral walls as presented in the term fetus and the young child; (4) the adult lateral walls with especial reference to some later developmental changes.
It is obvious that the fundamental structures to be considered in a study of the development of the lateral wall of the cavum nasi are:
- the nasal meatuses and the nasal conchae;
- the accessory furrows and the accessory folds (conchae);
- the anlages of the sinus paranasales.
The materials used in this investigation include the following:
a. Human embryos at successive ages from 21 days up to the fetus at term;
b. Fifty lateral nasal walls of new-born children;
c. Twenty lateral nasal walls of children, ranging in age from birth to 15 years;
d. One hundred and ﬁfty adult lateral nasal walls, ranging in age from 15 to 88 years;
e. Embryological and adult specimens of the lateral nasal wall of the cat, dog, muskrat, woodchuck, skunk, monkey, pig, sheep, and cow.
The lateral wall of the nasal cavity of human embryos, aged respectively 35, 43, 49, 58, 70, 83, 103, 120, 210, and 280 days, was modeled by the blotting-paper method. Some of the models were sectioned at appropriate planes to facilitate a more detailed study of parts. In a number of instances the nasal fossee were also reconstructed, in order to aid in a better understanding of certain developmental stages. Through the kindness of Mrs. Gage, who had previously modeled a 21-day human embryo, I had the privilege of studying this region at this early stage of development.
The ages of all the human embryos studied were determined by the Mall-method (Catalogue of the collection of human embryos in the anatomical laboratory of the Johns Hopkins University, Baltimore, 1904).
I wish to take this opportunity for expressing grateful acknowledgment to Professors Kerr, Kingsbury, and Tinker for helpful suggestions. I also wish to express my appreciation of the abundant material and other facilities placed at my disposal by the departments of Anatomy, and Embryology and Histology. To Professor and Mrs. Gage, for many courtesies extended during this piece of research, I wish to express thanks.
2. The Formation of the Nasal Fossae the Nasal Anlage
The nasal anlage apparently establishes itself about the third week of embryonal life as localized thickenings of the ectoderm. Kallius and Mihalkovics place the earliest trace of the nasal anlage at the beginning of the third week, and Bryce at the end of the
third week of embryonal life. Mrs. Gage refers to the nasal epithelium in a “three weeks human embryo.”
These thickened ectodermal or nasal areas are situated onboth sides of the outer surface of the wall of the fore—brain, just superior to the primitive oral fossa. Whether the nasal areas of the human embryo are at ﬁrst connected, and later undergo division into two distinctly separate halves, is not deﬁnitely known. The H-shaped nasal area of Mrs. Gage’s 21-day embryo seems signiﬁcant. She ﬁgures two lateral plates connected by an intervening bar of apparently similarly thickened ectoderm. Minot says: “It is possible that more exact observation will show that in all vertebrates there is at ﬁrst a single plate, which is early divided.” Doubtless this will remain a mooted point in man until a suﬂicient number of human embryos of the proper age fall into the hands of different observers.
Bedford found the thickness of the olfactory areas in swine embryos of 5 mm. length to be 0.075 mm. Kallius found that, while the general ectodermal thickness was 0.01 mm., the thickened nasal areas measured from 0.044 to 0.060 mm.
The nasal pits
During the fourth week the nasal areas become depressed— according to Mihalkovics at the end of the third week. This depression is not due to an invagination of the nasal areas, but it is passive and is caused by an increase in the thickness of the surrounding mesoderm. These ridges of thickened mesoderm around the nasal areas push the ectoderm into relief. In this manner each nasal area becomes surrounded by a fold, and is thus passively depressed. The folds are not complete but are deﬁcient inferiorly, and the thickening is most marked medially and laterally. The comparatively excessive medial and lateral thickening is thought by Kallius to be in anticipation of the later medial and lateral nasal processes. The nasal plates or areas thus become the olfactory or nasal pits, separated by a broad mass of tissue~the fronto—nasal process or the Stirnfortsatz of German embryologists.
The pits are primitively more or less pyriform in shape. The clubbed ends are directed somewhat medially and towards the vertex of the head, and the inferior extremities are directed somewhat laterally and towards the primitive oral fossa—the stomo~ daeum. As the pits deepen they seem to separate the inferior portion of the fronto—nasal process on both sides into medial and lateral parts—the anlages of the medial and the lateral nasal processes. During the latter part of the fourth Week, or early in the fifth week, the median portion of the fronto—nasal process undergoes further differentiation into a median or unpaired part, and two lateral or paired parts. The latter are globe—like and will be spoken of as the medial nasal processes (Processi globulares, His), and they form the immediate medial boundaries of the nasal pits. At the same time the lateral portions of the frontonasal projection grow caudally and form the lateral nasal processeswthe immediate lateral boundaries of the nasal pits, or the primitive lateral nasal walls.
Up to this time the nasal pits are not closed in inferiorly, but communicate freely with the primitive oral fossa. In other words, the nasal pits and the oral fossa represent in a sense a common cavity. At this stage of development the maxillary processes of the ﬁrst or mandibular arches grow ventrally and medially and abut—later fuse~—With the medial nasal processes (Processi globulares). This fusion closes in the superior boundary of the primitive oral cleft, and at the same time shuts off the path of communication between the nasal pits and the oral cavity, i.e., the nasal pits are closed in inferiorly (figs. 1 and 3). The coales— cence of the maxillary processes with the medial nasal processes forms the primitive inferior boundaries of the nasal pits; subsequently, however, the later extensions of the lateral nasal processes, medially and ventrally above the maxillary processes, meet and fuse with the medial nasal processes, to form the immediate inferior boundaries of the nasal pits (ﬁg. 1). His has also pointed out, in case of arrested development in this region, that at times the lateral and medial nasal processes fuse, but that the maxillary process, on one or both sides, remains short and does not develop sufficiently to fuse with the medial nasal process as it normally does. In such cases the nasal pits are closed in below and are separated from the oral cavity, yet clefts exist between the medial nasal and the maxillary processes.
FIG. 1 (X 30) Drawing of a reconstruction of portion of the head of an embryo aged approximately 35 days (Human embryo, No. 6, Cornell University series, slides 50-57 inclusive). The figure represents a cauzlo-ventral view of the reconstruction.
Note the wide separation of the nasal fossae at this time, and that the fossac do not communicate with the mouth cavity. The maxillary and the medial nasal processes have fused, thus shutting off the nasal pits from the mouth cavity. The lateral nasal processes have not yet fused with the medial nasal processes. The external nose has not yet taken on any deﬁnite shape. Note the points for the primitive choanae and the extent of the primitive palate.
FIG. 2 (X 45) Drawing of a reconstruction of the left nasal fossa. The reconstruction is from the same embryo as that in ﬁg. 1, and the plane of section is indicated by the line drawn over the left nasal fossa in ﬁg. 1. Note the very simple lateral nasal wall at this stage of development and compare it with the medial wall. In a. short time the lateral wall becomes much more complex and the medial wall relatively less so.
Figs. 3, 4, 5, (33.2) Photomierographs of frontal sections through the head of an embryo aged approximately 35 days (Human embryo, N o. 26. Cornell University series, slides 19 and 20). The sections are in the region of the primitive nasal fossae. Section fig. 3 is the most Ventral and section fig. 5 the most dorsal of the three.
FIG. 3. Note that in the region of the coalescence of the medial nasal and the maxillary processes there is no intervening ectoderm. Fusion is complete and absolute, in that the mesenchymal tissue of the maxillary and medial nasal processes is continuous. _
FIG. 4. Note the ectodermal strands between the medial nasal and the maxillary processes; the mesenchymal tissue of these processes is not continuous. Compare this condition with fig. 3.
FIG. 5. On both sides the two layers of epithelium, oral and nasal, have become attenuated and thinned o11t to represent single layers of cells. These are the hucconasal membranes which ultimately rupture to establish the primitive choanae.
Fus1'an, = coalescence between the maxillary and the medial nasal processes; Med. nas. proc., = medial nasal process; Mam. proc.. = maxillary process; Memb. buc., = membrane bucconasalis.
Fm. 6 (X 18) Photomicrograph of a frontal section through the ventral portion of the nose of an embryo aged approximately 49 days (Human embryo, No. '28, Cornell University series, slide 40).
Shows the epithelial plugs occluding the nares. This is a rather common condition during the latter part of the second month and throughout the third month. It also occurs after this period, as I have seen it in a 120 day-embryo. Lateral Wall of the Cavum Nasi in Man. 621
Fusion also takes place laterally between the maxillary and lateral nasal processes, and from the strands of ectodermal tissue caught between the edges of the coalescing processes, the nasolacrimal ducts develop, i.e., the ectodermal strands acquire lumina. These ducts will again be referred to in connection with their apertures on the lateral nasal walls. The ducts usually establish communications with the inferior nasal meatuses at about term. This may however be longer delayed.
For some time the lines of fusion of the maxillary and the lateral nasal processes with the medial nasal processes are represented by strands of ectodermal tissue. These ectodermal fusion—lines soon disappear ventrally and are replaced by indifferent mesenchyme, i.e., the mesenchymal tissue of the maxillary and the lateral nasal processes becomes continuous with that of the medial nasal processes. Fusion in this manner becomes permanent and absolute (ﬁg. 3). Farther dorsally the ectodermal tissue does not wholly disappear, but strands of the latter tissue remain between the abutting processes. I n these positions the primitive choanaa ultimately become established (ﬁgs. 2 and 4).
The primitive nasal fossae
By this time (35-day embryo) the nasal pits have deepened dorsally, and more or less superiorly and inferiorly. The olfactory organ is now represented by two blind pouches lying in the mesenchymal tissue above the oral cavity. The pits have now developed sufﬁciently so that they may be termed the primitive nasal fossae. The fossae communicate freely with the exterior by means of the nares, but, in the absence of choanae, they end blindly at their dorsal and inferior terminations (ﬁg. 2). They are rather widely separated at this time (ﬁg. 1). A reference to ﬁg. 2 will show both the lateral and medial walls of the left nasal fossa of a 35-day embryo. It will be noticed that the lateral wall is extremely simple, presenting merely a plane surface. The medial or septal wall is slightly grooved and the groove overhung by a fold. This is the anlage of the organon vomeronasale (J acobsoni). Note also that the fossa ends blindly and that there is no connection between the oral and the nasal fossa at this time. The point of the primitive choana (posterior naris) is nearly thinned out sufficiently to represent the membrana bucconasalis (ﬁg. 5).
The primitive choanae
The dorsal extension of the blind pouches or primitive nasal fossae continues until the ectoderm of the nasal fossae meets the ectoderm of the oral fossa. We have now in these positions merely thin membranes composed of two layers of abutting epithelium— nasal and oral——separating the dorsal portions of the primitive nasal fossaefrom the oral cavity. These membranes, which have been carefully studied, and named by Hochstetter, the “Membranaebucconasales,” (ﬁg. 5) become so attenuated and thinned out that they ﬁnally rupture. The membranes may rupture at the same time or each may rupture independently of its mate.
According to the embryos studied for the substance of this paper the bucconasal membranes rupture from the 35th to the 38th day of embryonal life. Sudler found connection between the oral and nasal fossae in a 5-weeks embryo. Hochstetter found in an embryo of “ 11 mm. lang bei 9 mm. Kopflange” that the nasal fossae ended blindly dorsally, and in an embryo of “15.5 mm. Lange und 10 mm. Kopflange,” the bucconasal membranes were broken through. He, however, found that the membrane was rather excessive on one side, apparently indicating recent rupture. The approximate age of these embryos would be 33 and 39 days, respectively. Kolliker places the time of establishment of the primitive choanse “in 'der zweiten Halfte des zweiten Monates.” The apparent discrepancy in the time at which the bucconasal membranes rupture is doubtless due to different methods of determining the age of embryos.
As a result of the rupture of the bucconasal membranes we have established two openings~—the primitive choanae (primitive Gaumenspalten, Dursy; innere Nasengange, innere Nasenlocher, Kolliker). There is thus established in man for a second time a commnication between the oral and the nasal fossae. The hitherto blindly ending nasal fossae now communicate not only with the exterior by means of the nares, but also with the mouth cavity by means of the primitive choanae.
Epithelial plugs in the nares
When ﬁrst formed the nares communicate freely with the exterior, but shortly afterwards, say about the fortieth day of embryonal life, the lumina of the nares in very many cases become ﬁlled in with epithelial plugs (ﬁgs. 6 and 7). This plugging which is due to a proliferation of the epithelial cells, seems to take place some time after the fusion of the medial and lateral nasal processes. In some cases the plugging is absolute, and in others deviating passages through the plugs may be seen. Sometimes the plugs are more or less fenestrated. I ﬁnd plugging rather frequent from the fortieth to the sixtieth day. I have, however, seen it in a 120-day embryo. The passages (nares) are apparently later opened by a shedding of the epithelial plugs rather than by a resorption of the cells——probably both factors are involved. As evidence of a shedding of the epithelial plugs we frequently ﬁnd shreds of epithelial masses extruding from the nares.
The primitive palate
With the formation of the primitive choanae we have also established the primitive palate, i.e., the portion of the roof of the oral fossa extending from the primitive choanae to the nares. This condition is, however, of short duration because the deﬁnitive palate soon begins to form, and the lateral walls of the nasal fossae thus become limited inferiorly. In the formation of the deﬁnitive palate the nasal fossae appropriate a considerable portion of the primitive oral cavity. This is readily understood when we recall the superior boundary of the primitive oral cavity dorsally. Ventrally the mouth cavity is bounded superiorly by the primitive palate, but dorsally the mouth cavity extends into the future nasal cavity until the formation of the deﬁnitive palate establishes a roof for the mouth cavity dorsally (ﬁgs. 8, 9, 11, 13, 14, and 15).
The formation of the deﬁnitive palate
A reference to ﬁgs. 10, 13, 14, and 15 will indicate the stages in the formation of the deﬁnitive palate, and the manner in which the lateral nasal wall becomes limited inferiorly. The ﬁrst step in the production of the deﬁnitive palate is the appearance of the palatal ridges. These are more or less wedge—shaped processes which grow caudally and somewhat medially from the medial sides of the maxillary processes. The palatal processes appear from the forty-ﬁfth to the forty-eighth day of embryonal life, and at ﬁrst hang almost vertically towards the mouth cavity, on either side of the tongue (ﬁg. 13). They extend from the line of union between the medial nasal and the maxillary processes, where they are continuous with the primitive palate, dorsally to the wall of the pharynx, where they are continuous with the palato-pharyngeal folds. The palatal processes limit the lateral walls of the cavum nasi inferiorly.
It will be noticed that the tongue is at ﬁrst between the palatal processes, z'.e., the processes extend below the level of the dorsum of the tongue (ﬁgs. 10 and 11). Soon the tongue sinks and comes to occupy a lower position in the mouth cavity. With this change of the tongue the palatal processes become rotated from an almost vertical and sagittal plane to a horizontal plane (compare ﬁgs. 13 and 14). The processes now shortly meet in the median plane above the tongue, and fuse from before backwards along the opposed edges. In this manner the separation of the nasal fossae from the mouth cavity is made complete and permanent. However in the ventral portion of the palate, where the palatal processes do not come in contact with each other (due to the interposition of the tissue separating the primitive choanae) the separation of the nasal cavity from the mouth cavity is not entirely complete. This is brought about by the medial nasal processes uniting and extending dorsally in the roof of the mouth cavity as the inter—maxillary process. The latter process projects farthest dorsally in the median plane, and on its lateral borders it is met by the ventral ends of the palatal processes. At these contact points the incisive canals are formed, and the latter at times serve as a means of permanent communication between the oral and nasal cavities. The lumina of the incisive canals are, however, generally obliterated early in life.
Explanation of Figures
Figs. 7 to 12 (X 10.5) Photomicrographs of frontal sections of the head of an embryo aged about 43 days (Human embryo, No. 3, Cornell University series, sections 406, 380, 365, 360, 350, 325).
Note the plugging of the nares in ﬁg. 7, and that the conchal anlages have no cartilage in them at this age (ﬁgs. 8—11). The mesenchymal tissueis, however, already undergoing condensation in anticipation of cartilage in the regions of the nasal septum and the lateral nasal walls. Compare this condition or pre-cartilage stage with ﬁgs. 16 to 20, and with ﬁgs. 32 to 38. Note the relation of the tongue to the palatal processes in ﬁgs. 8 to 12.
The section shown in ﬁg. 7 is the farthest ventral and that shown in fig. 12 the farthest dorsal in the series.
I’. pal., = processus palatinus; Eth. fold, = ethmoidal fold; Maw. fold, = maxillary fold.
FIG. 13 (16.6) Drawing of a reconstruction of the lateral wall of the nasal eavity of an embryo aged approximately 43 days (Human embryo, N0. 3, Cornell University series, sections 300-420 inclusive).
Shows the vertical position of the palatal process at this time. The deﬁnitive palate is not yet formed. Note also the primitive concha inferior (Max. fold) and that it occupies the greater portion of the lateral wall at this early stage. The primitive ethmoidal fold (Eth. fold)—the anlage of the ethmoidal conchaeis very rudimentary at this time.
Eth. fold, = ethmoidal fold; Max. fold, = maxillary fold; P. pal., = palatal process.
Fig. 14. (X 16.6) Drawing of a reconstruction of the lateral wall of the nasal cavity of an embryo aged approximately 49 days (Human embryo, No. 28, Cornell University series, slides 40-51 inclusive).
Compare horizontal position of the palatal process with the process in ﬁg. 13. The ethmoidal region now has two folds well marked, and 21 rudimentary third presents in the superior and dorsal portion of the lateral wall. The concha nasalis inferior occupies comparatively less of the lateral wall. Ventrally it will be noticed that the reconstruction does not include all of the lateral Wall. The ventral portion of the primitive palate is, therefore, not represented in the reconstruction.
Fig. 15. (X 6.6) Drawing of a reconstruction of portion of the right wall of the nasal cavity of an embryo aged about 105 days (Human embryo, No. 43, Cornell University series, slides 1-90 inclusive).
The deﬁnitive palate is completed and the choana has assumed the adult position. Compare this with ﬁgs. 2, 13, and 14. The ethmoidal region now presents four conchae, the highest of which is not yet well differentiated. Note the marked lobule in the region of the knee of the concha nasalis media.
The permanent choanae and the permanent nasal fossae
Coincidently with these changes in the formation of the nasal fossae, the primitive choanae elongate and ultimately occupy their deﬁnitive position, and thus become the permanent or secondary choanae. The changes in the formation of the permanent choanae also aid materially in increasing the ventrodorsal extent of the nasal cavity. The latter now begins to take on its adult form. The nasal septum which already has separated the nasal fossae ventrally, rapidly fuses with the palate in the median plane, t'.e., along the line of fusion of the palatal processes. In this manner the cavum nasi is divided into the nasal fossae. This division takes place from before backwards.
Before the ﬁrst appearance of the palatal processes as inferior boundaries of the nasal fossae, the lateral walls of the fossae have begun in a simple manner to form the complex conﬁguration which characterizes the adult lateral nasal walls.
3. The Development of the Lateral Wall of the Cavum Nasi
In the preceding paragraphs we considered the successive stages in the establishment of the nasal cavity, from the thickening of the ectoderm to form the nasal anlage, to the formation of the nasal fossae. We noted the extreme simplicity of the lateral wall of the nasal cavity during the early stages of development. With these considerations on the various developmental stages of the nasal fossae and the early condition of the lateral wall as a basis, we may now to better advantage follow in detail the stages in the formation of the various structures found on the lateral wall. We will, therefore, pass, in order, from the very simple lateral wall of the early embryo to the complexly conﬁgured wall of the term fetus.
The formation of conchal anlages
A reference to ﬁg. 2 will indicate the extremely simple lateral wall of the nasal fossa of a 35-day embryo. It will be noticed that there is no evidence of the later complexity and conﬁguration caused by the nasal conchae, the nasal meatuses, the accessory conchae and furrows, and the anlages of the paranasal chambers. In fact the medial or septal wall is more complicated at this time than is the lateral wall—this standing in marked contrast to later conditions (compare figs. 2, 13, 14, and 21).
Some days later (38- to 40-day embryo) the inferior portion of the lateral wall immediately superior to the primitive palatal processes begins to bulge towards the lumen of the nasal fossa. In fact this bulging for a brief time occupies nearly the whole of the vertical portion of the wall, and approximately the dorsal two-thirds. This fold represents the anlage of the concha nasalis inferior (maxilloturbinal) (ﬁg. 13). Shortly after this (40 to 43 days) a second fold appears superior and somewhat dorsal to the ﬁrst one. The former (ethmoidal fold) is placed in the superior and dorsal angle of the lateral wall. It seems also to extend up on the nasal septum at this point, and some of its prominence is really due to septal tissue. This fold is the anlage of the conchae nasales ethmoidales, and in position and relations represents the concha nasalis media (Ethmoturbinale I, Peter; zweite Haupt— muschel, Killian; untere Siebbeinmuschel, Zuckerkandl; Basotur— binale, Schonemann). The fold of the agger nasi (nasoturbinal) can hardly be said to be in evidence at this early stage. It appears later, ventral and superior to the concha nasalis inferior, and ventral to the concha nasalis media.
Views as to the genesis of the primitive nasal folds and furrows
From the above we gather that the lateral nasal Wall is early thrown into ridges or folds which are bordered by furrows or depressions. Just how these primitive folds (primitive conchae) and furrows (primitive meatuses) of the lateral wall are formed is interpreted differently by various writers. While at ﬁrst thought the views held seem widely divergent, they appear less so after we carefully analyze them. Some of the theories entertained are, however, without foundation.
It was at one time held by some observers that the folds were due to cartilaginous strands pushing the lateral nasal wall medially in the positions of the folds. This theory is, however, not tenable because the folds (primitive conchae) are invariably present some time before cartilage is found in them. Only later does some of the indifferent mesenchyme contained in the folds change into cartilage; therefore it can have no connection whatever with the establishment of the primitive folds (conchae).
Legal and Schonemann think that the folds are elevations left by excavations of furrows on the lateral nasal wall. Legal in offering this explanation especially referred to the inferior nasal concha. Later Schonemann concludes “dass nicht die Legalsche Angabe iiber die Bildung der unteren Muschel vollig zu Recht besteht, sondern dass auch fiir die samtlichen anderen Muscheln ein ahnlicher Bildungsmodus angenommen werden muss.”
Mihalkovics, according to Schonemann, holds that the folds are at ﬁrst “frei vorwachsende Duplikaturen der Schleimhaut.” Glas, who investigated this ﬁeld in rats, comes to the following conclusion: “Der Bildungsmodus der Muscheln ist die Resultierende zweier Komponenten: (1) des Auswachsens in die Wandpartien einwachsender Epithelleisten (Fissuren), (2) des Vorwachsens bestimmter Wandpartien.”
After a study of these early conditions I am led to believe that the ﬁrst change in the lateral nasal wall from a more or less even surface (fig. 2) is the production of very shallow grooves, the latter appearing inferior and superior to the position of the primitive concha inferior. These shallow grooves at once throw into slight relief the greater portion of the lateral nasal wall——the anlage of the concha nasalis inferior (maxilloturbinal). I believe that the mesenchymal tissue contained within this primitive fold almost simultaneously undergoes proliferation, thus aiding in early making the fold more prominent. The mucous membrane over the fold may also become thickened, but according to my observations this thickening for the primitive concha inferior is slight. I cannot agree that the formation of a well marked maxillary fold or primitive concha nasalis inferior is wholly due to the formation and deepening of the bordering furrows but, as stated before, I believe that the formation of very shallow grooves is the primitive step in conchal formation. The proliferation of the mesenchyme (probably also the mucous membrane to some extent) aids materially in causing the primitive concha inferior to bulge into the lumen of the nasal fossa, and the bordering furrows to become passively deeper (figs. 10 and 11).
The ethmoidal fold appears next in the extreme dorsal and superior portion of the nasal fossa, in the angle formed by the lateral wall and the nasal septum in this position (ﬁgs. 11 and 13). Since the primitive concha inferior (maxillary fold) takes up the greater portion of the lateral wall at this time there is little room for the primitive ethmoidal fold (ﬁg. 13). For this reason the latter fold arises in part from the septum. Later the nasal fossa increases in the dorsosuperior direction, and with this the primitive ethmoidal fold passively migrates from the septum. The mucous membrane over the ethmoidal fold is as a rule thickened, and this thickening causes the primitive fold to show up well in frontal sections (ﬁg. 11). This, however, does not detract from the statement that the groove between the ethmoidal amd maxillary folds is present, at least to some extent, before the folds havegained any appreciable bulging. Later we have a proliferation of the mesenchyme and a deepening of the furrow (primitive meatus nasi medius) inferior to it, hence the ethmoidal fold becomes more prominent. Gradually in place of the single ethmoidal fold we have, with the increase of the nasal fossa in the dorsosuperior direction, the establishment of anlages of the individual ethmoidal conchae—this, as a rule, taking place in order from the most caudal to the most cephalic ethmoidal concha (ﬁgs. 13, 14, 15, and 21).
As may be inferred from the above, the ethmoidal region on each side presents but for a brief time a single fold (ﬁg. 13). As the nasal fossa enlarges superiorly and dorsally there is a differentiation in this region into two folds (ﬁg. 14)-—this change occurring approximately from the forty-eighth to the ﬁftieth day of fetal life. A later stage, 95 to 100 days, shows three well formed ethmoidal conchae (ﬁg. 15). By the fourth month of fetal life the conchal ﬁeld shows from three to four ethmoidal conchae, besides the concha inferior. Fetuses from the seventh month to term will, if carefully examined, show from three to five ethmoidal conchae (ﬁgs. 21 and 30). Of course in each case a. corresponding number of furrows or meatuses are established—some of the meatuses, however, being very rudimentary. After birth the ethmoidal conchae and meatuses become reduced in number. This reduction is not carried so far in some cases as in others-—thus accounting for the supernumerary or additional conchae and meatuses of many adult noses. Doubtless the number of ethmoidal conchae that are differentiated before birth have an important bearing on the number of conchae that may be present in an individual casethis is probably just as important a factor in determining the num ber of adult ethmoidal conchae as is the retrogressive change of reduction.
The early changes in the meatus nasi medias
Thus far only the superﬁcial aspects of the lateral nasal wall, with especial reference to the development of folds and furrows (conchae and meatuses), have been considered. The general plan of these conchae and meatuses will be considered in detail in subsequent paragraphs. If now we return to a 40- to 50-day embryo and examine the portion of the middle meatus operculated by the middle nasal concha, we will notice that the lateral wall of this meatus is perfectly even (ﬁg. 16). This study is best made by an examination of serial frontal sections through this region of the nose. This same region in an embryo aged from 58 to 60 days will indicate the beginning formation of the complicated nature of the meatus nasi medius——the most complex of all the meatuses. This change in the middle meatus is heralded by the appearance of a somewhat crescentic-shaped fold of mesenchyme and mucous membrane, set off by a slightly earlier grooving immediately superior to the fold. The latter has its free and rather sharp border directed superiorly and dorsally, and is the anlage of the processus uncinatus. The furrow immediately superior to the fold is the primitive infundibulum ethmoidale (ﬁg. 18). It will be noticed that the furrow communicates rather freely with the meatus nasi medius through a rather widely open cleftthe hiatus semilunaris.
(‘lg/I wmmmu’ _ between [he nasal and oral ctmiliea brgfare : , completion: 0]‘ Ihe 49- -‘ “ l’mrmu.; palrzlimls ﬁnilirr palate
Fig. 16. (X 26.6) Outline drawing of a frontal section of the nasal cavityrof an embryo aged approximately 49 days (Human embryo, No. 28, Cornell University series, slide 48). The nasal and oral cavities are in communication with each other at this point, i.e., the palatal processes have not as yet coalesced in the median plane in the formation of the deﬁnitive palate. Note also the simple lateral wall of the middle nasal meatus—-compare with fig. 18.
If now we examine a frontal section of a somewhat later embryo we will notice that the infundibulum ethmoidale early tends to develop beyond its primitive limits, and to pouch towards the ventral and superior portion of the meatus nasi medius, here ending blindly. This early, blind, Ventral and superior extension of the infundibulum ethmoidale has been erroneously considered by some writers as the primitive sinus maxillaris (ﬁg. 32). Of the bulla ethmoidalis there is nothing to be seen at this time.
About the seventieth day there is a slight, sometimes a comparatively extensive, pouching or evagination of the mucous membrane from the depth of the infundibulum ethmoidale—thus establishing the anlage of the sinus maxillaris. Shortly after this we have the ﬁrst evidences of the bulla ethmoidalis appearing superior and lateral to the processus uncinatus——this in the form of very low accessory folds or conchae. By the beginning of the fourth month of fetal life the folds of the bulla are fairly well formed. At the end of the fourth month the folds with the bordering accessory furrows are in many cases well outlined (ﬁg. 18). From some of the accessory furrows the so-called middle group of ethmoidal cells develop, and in a sense the former are the anlages of the latter structures. At a comparatively early stage we have evidences of a beginning extension of the middle meatus in a ventral and superior direction. This is the anlage of the recess, which Killian in later fetuses terms the ‘Recessus frontalis’ and it is in reality the ﬁrst step in the formation of the sinus frontalis and the most ventral of the anterior group of ethmoidal cells. The accessory folds and furrows, and the frontal recess of the middle meatus will be considered in detail in a subsequent por tion of this paper.
Fig. 17. (X 10) Outline drawing of a frontal section through the nose of an embryo aged 120 days (Human embryo, No. 42, Cornell University series, slide 29).
At this plane of section the processus uncinatus is fused with a. frontal fold, and the infundibulum ethmoidale ends blindly. Compare this ﬁgure with ﬁg. 18. In the latter ﬁgure the plane of section is farther dorsal.
The early changes in the meatus nasi superior
With the appearance of the accessory folds (conchae) and the frontal recess of the middle meatus, we have the establishment, in very many cases, of the anlage of an accessory fold (concha) on the lateral wall of the superior meatus. This fold early tends to form very shallow recesses superior and inferior to it, and occasionally it has been mistaken for the superior nasal concha (ﬁg. 19). From the superior and inferior recesses, and from the Ventral and superior extremity of the superior meatus, most of the posterior group of ethmoidal cells develop—a matter which will be taken up subsequently. Frequently a posterior ethmoid cell develops from the meatus nasi suprema I. The latter meatus, however, is present in only 62.5 per cent of my adult specimens
The early changes in the superior and dorsal portion of the nasal fossae
A frontal section through the dorsal portion of the nasal cavity in a three-months embryo will already indicate the manner of constriction of a portion of the dorsal and superior part of the nasal fossae in the formation of the early anlages of the sinus sphenoidales. In a 120-day embryo the sphenoidal-sinus anlages are well advanced, but have not reached, or at least not extended into, the body of the developing sphenoid bone. The lateral nasal plates of cartilage more or less overhang the sphenoidal— sinus anlages (ﬁg. 20).
The number of ethmoiddal conchae and meatuses that are diﬁerentiated before birth
As to the number of ethmoidal conchae and meatuses that are differentiated during the latter months of intrauterine life conﬂicting opinions are held. The meatus inferior and the concha inferior are constant, hence they will not be considered in the present connection.
Zuckerkandl states that three and at the highest four ethmoidal meatuses are formed (including the meatus medius). This would indicate three and at the highest four ethmoidal conchae. In reference to the latter he says: “Drei Siebbeinmuscheln reprasentieren . . . die typische Faltungsweise des Siebbeines.” Killian, whose researches on this point are extensive, states that in fetuses of the ninth to the tenth month, ﬁve and even six ethmoidal meatuses (Hauptfurchen) are present. He also ﬁnds a corresponding number of ethmoidal conchae (Hauptmuscheln), but includes among the number, as his “erste Hauptmuschel,” the agger nasi (nasoturbinal) plus the processus uncinatus. Killian comes to the following conclusion: “Mit dem, was das auf
Fig. 18. (X 10) Outline drawing of a frontal section through the nose of the same embryo as that in ﬁg. 17. The plane of section in this ﬁgure (slide 40) is farther dorsal, and is in the region of the bullar folds.
The processus uncinatus projects free at this plane of ection, and the infun— dibulum ethmoidale communicates rather freely with the meatus nasi medius. The cartilage of the processus uncinatus is not continuous with the cartilage of the lateral plate at this 1evel—compare this with the cartilage of the processus uncinatus in ﬁg. 17.
merksame Studium meiner Preparate ergiebt, stimmen die Beobachtungen an meiner ganzen Material ﬁberein, wobei ich bemerke, dass die erste, zweite und dritte Hauptfurchen fast regelmassig vorkommen und dass die vierte in ﬁber 30 Fallen, die fiinfte und sechste in noch einigen weiteren Beispielen vertreten sind.” Kallius holds that seldom are all six furrows differentiated. Mihalkovics says that “Knorpelige Muscheln sind beim Menschen im embryonalen Leben stets 4 vorhanden, oft auch 5.” The latter, however, includes among this number the concha nasalis inferior, which has not been done by the other writers mentioned, since they considered the ethmoidal region only.
After an extended study of the ethmoidal region in fetuses, I ﬁnd that there is more or less uniformity up to the fourth month. However during the latter half of fetal life there is indeed great variation in the number and form of the ethmoidal conchae and meatuses. Notwithstanding this I think that careful analyses indicate a general plan more or less common to most ethmoidal regions—-some specimens differing here and others there from the plan. Occasionally some specimens differ so markedly from this general plan that they are diﬁicult of comparison.
Doubtless the personal equation is quite a factor in determining the number of _ethmoidal conchae. In many cases some of the conchae are so rudimentary that one observer might not consider the under-developed folds as individual conchae, yet another observer would include them among the number.
I find by careful study of the ethmoidal region in a series of specimens from late fetuses that ﬁve ethmoidal conchae are not uncommon, however the most superior and dorsal conchae may be but faintly outlined. We occasionally ﬁnd all ﬁve conchae well marked (ﬁg. 21). In this respect my observations agree with those of Killian—he giving six as his highest number of ethmoidal conchae. The apparent discrepancy in number is due to the fact that he (Killian) names the agger nasi (nasoturbinal) plus the processus uncinatus as his ‘erste Hauptmuschel.’ On the other hand I do not do this, but consider his ‘zweite Hauptmuschel’ as my concha nasalis media. I ﬁnd four ethmoidal conchae very frequent indeed, in fact fully 65 per cent of later fetuses, according to my series of specimens, present four (ﬁg. 26). It must, however, be remembered that some of the conchae or folds are extremely rudimentary, nevertheless they must be taken into consideration when analyzing the ethmoidal region. Occasionally some specimens show a low degree of differentiation and possess but three ethmoidal conchae (ﬁg. 28).
It is indeed difﬁcult to say whether in the latter cases the progressive changes (differentiation) have not been carried so far as in some others, or whether retrogressive changes (coalescence of two or more conchae with obliteration of the intervening furrows) took place at an earlier time. The latter is doubtless an active process after birth, because we rarely ﬁnd more than three ethmoidal conchae in the adult. It is, therefore, quite possible that retrogressive changes are instituted much earlier in some cases, and that the ethmoidal regions which have a comparatively small number of conchae in the late fetus, originally possessed a larger number of folds. I, however, believe that in the majority of these cases the differentiation in the ethmoidal region is not carried so far as in some others, hence a smaller number of ethmoidal conchae.
Fig. 19 (X 10) Outline drawing of a frontal section through the nose of the same embryo as those in figs. 17 and 18. This section (slide 67) is in the region of the accessory concha of the meatus nasi superior, hence is farther dorsal than that in ﬁg. 17.
Shows how the crista suprema of the concha media aids in forming the recessus inferior of the rneatus superior. Compare the meatus superior of this section with the Ineatus medius of section, fig. 18.
Whatever the number of ethmoidal conchae may be, there is a corresponding number of meatuses or furrows; '£.e., each concha more or less overhangs a furrow or meatus. This overhanging is especially marked in the meatus nasi medius. Killian gives six as his highest number of ‘Hauptfurchen’—this would place a meatus dorsal and superior to the most cephalic concha present. I, however, prefer to think of this region as belonging to the recessus sphenoethmoidalis. The latter because it corresponds to the position of the adult recessus sphenoethmoidalis; also that after birth we do not usually think of the meatus nasi as being superior to, but inferior to the corresponding conchae nasales. The recessus sphenoethmoidalis, however, is very closely related to the meatus nasi suprema I, and in the absence of the latter with the meatus nasi superior.
Fig. 20. (X 10) Outline drawing of a frontal section through the dorsal portion of the nasal cavity. The section (slide 9]) is from the same embryo as are those represented in figs. 17, 18, 19. Note how the dorsal and superior portions of the nasal fossae establish the anl-ages of the sinus sphenoidales.
Owing to the comparatively large number of ethmoidal conchae and Ineatuses present in the nose of the late fetus in comparison to adult conditions, it will be necessary for the sake of description to adopt some nomenclature sufficiently extensive to cover the extreme cases one meets at this time.
Zuckerkandl’s nomenclature is not extensive enough to cover the fetal ﬁeld in all cases. He designates the ethmoidal conchae as “untere, mittlere, obere, und Vierte (oberste) Siebbeinrnuscheln.” He speaks of the ethmoidal meatuses as “inferior, superior, und suprema Fissurae ethmoidales.” He, however, complicates his nomenclature by his views on the “Vierte (oberste) Siebbeinmuschel.” He makes the following statements:
- “In 6.7 Percent der Falle tritt bei Kindern und Embryonen noch eine Vierte Siebbeinmuschel auf, die sich zwischen die mittlere und obere Concha ethmoidalis einschiebt. . . Vierte Siebbeinmuschel (Concha suprema), begrenzt: unten von der Fissura ethmoidalis suprema, oben Von der Siebplatte.”
There is doubtless a discrepancy in the above statements. If the “Vierte (oberste) Siebbeinmuschel” inserts itself (“einschiebt”) between the “mittlere und obere Concha ethmoidalis,” then the furrows or meatuses that border it are his (Zuckerkand1’s) “superior und suprema Fissurae ethmoidales,” and the “obere Siebbeinmuschel” would be between his “Fissura ethmoidalis suprema” and the “Siebplatte.” The reader will at once notice the difficulty encountered in attempting to compare this with other nomenclatures.
Killian adopts a nomenclature to cover, according to my specimens, all cases, by naming the ethmoidal meatuses, including the meatus medius, ‘Hauptfurchen 1-5;’ and the ethmoidal conchae, ‘Hauptmuscheln 1.5.’ He, however, includes among his “Hauptmuscheln” the agger nasi (nasoturbinal) plus the processus uncinatus as his ‘erste Hauptmuschel,’ which has not been done in this paper.
Peter also covers the ﬁeld by designating the ethmoidal conchae ‘Ethmoturbinalia1.5.’ The latter does not include Killian’s ‘erste Hauptmuschel’ among this number.
Schonemann speaks of the concha media as the ‘Basoturbinale,’ and Paulli in an exhaustive study refers to all the major nasal conchae as ‘Endoturbinalien,’ in contradistinction to the accessory conchae which he designates as ‘Ektoturbinalien.’
The general text—books of anatomy, also the BNA (nornina anatomica, Basel), offer nomenclatures sufficient for practically all adult conditions, but not for the late fetal stage. In order not to depart too far from the general texts on anatomy and the BNA, yet offer for late fetal conditions a sufficiently comprehensive nomenclature, I will in subsequent paragraphs use the following names for the several nasal conchae and ineatuses.
The nomenclature offered is not necessary for all cases, nevertheless it is essential to have a terminology that covers not only the adult, but also the extreme fetal conditions one frequently meets.
Nomenclature used in this paper:
Meatus nasi. Conchae nasales. Meatus nasi inferior, Concha nasalis inferior, Meatus nasi medius, Concha nasalis media, Meatus nasi superior, Concha nasalis superior, Meatus nasi suprema I, Concha nasalis suprema I, Meatus nasi suprema II, Concha nasalis suprema II, Meatus nasi suprema III. Concha nasalis suprema III.
The nasal meatuses and conchae as seen during the latter stages of intrauterine life
The nasal meatuses and conchae of the fetus of the latter half of intrauterine life may now be considered in detail. The ethmoidal region is rather complex in construction, and with the accessory folds (conchae) and furrows, the anlages of the paranasal chambers, and the conchae and meatuses, offers an interesting ﬁeld for study from the second month on to term. The meatuses will be taken up first for detailed study, followed by the nasal conchae. After this the accessory folds (conchae) and the accessory furrows of the meatuses will be considered; ﬁnally the anlages of the paranasal chambers.
The nasal meatuses
The meatus nasi inferior. The meatus nasi inferior is one of the first meatuses to become well established. It is primitively formed between the anlage of the concha inferior and the primitive processus palatinus. Later, with the fusion of the two palatal processes in the median plane to form the deﬁnitive palate, the meatus inferior comes to occupy the position between the concha inferior and the floor of the nasal fossa. The ductus nasolacrimalis connects with the meatus inferior approximately at term. A reference to ﬁg. 37 will, however, show a frontal section of the left nasal fossa of a term fetus in which the barrier between the meatus inferior and the ductus nasolacrimalis is still intact, z'.e., the duct has not acquired a lumen in the region of the meatus inferior. Finally there are two layers of abutting epithelium, one nasal and the other that of the duct, forming the barrier. The membrane now seems to thin out and to become attenuated, ultimately rupturing; in other words the duct becomes patent at this point. This attenuation of two layers of abutting epithelium, ultimately resulting in rupture, in order that communication between two cavities may be established, reminds one somewhat of the attenuation and rupture of the membrana bucconasalis.
The meatus nasi inferior is otherwise simple and offers no conditions that warrant a further consideration at this time.
The meatus nasi medius, superior, suprema I, suprema II, suprema III. The ethmoidal meatuses, including the meatus medius—since they have many things in coinmon—may for the time be considered together. It must be recalled that in many cases the meatus suprema I, II, and III are extremely rudimentary, and are merely very shallow, short grooves. Again in many instances the meatus nasi suprema II and III are not at all differentiated. The meatus nasi suprema I is the most constant of the supreme meatuses. While we must follow some general type for the sake of description, it does not necessarily indicate that all specimens agree in their entirety.
The ethmoidal meatuses all converge at their inferior and dorsal extremities in the region of the angle formed by the junction of the anterior and inferior surfaces of the body of the sphenoid bone (ﬁg. 21). These meatuses in a general way possess knees or bends, thus presenting ascending and descending rami. These bends are best marked in the middle and superior meatuses. It is a constant condition in the middle meatus, and a fairly large number of specimens show a well marked ascending ramus for the superior meatus. The remaining meatuses when present, however, do not have well marked ascending rami. In fact very many specimens give no evidence whatever of individual ascending rami for the meatus suprerna I, II, and III (ﬁg. 23). In a general way it may be stated that the differentiation of ascending rami becomes gradually less marked as we pass from the meatus medius to the meatus suprema III (ﬁgs. 21, 23, and 25).
The ascending rami. The ascending ramus of the middle meatus is directed rather obliquely, in a ventral and superior direction — this is less so for the corresponding ramus of the superior meatus. As we pass from the superior meatus to the supreme meatus III we ﬁnd a rapid change in direction of the ascending rami to a more or less vertical plane, 72.6., the ascending rami more nearly Vertical to the cribriform plate of the ethrnoid bone. We may, therefore, say——When ascending rami are differentiated~—that as we proceed from the meatus medius to the meatus suprema III, there is a gradual change in direction of the ascending rami from an oblique to a more or less vertical plane (ﬁg. 21).
In fig. 21 we have the representation of a specimen which presents an ascending ramus for each corresponding meatus. The ascending rami of the supreme meatuses, II and III are, however, not marked, in that the two latter meatuses seldom have well developed knees. In ﬁg. 22 the ascending rami are indicated merely by very shallow, short grooves near the cribriform plate of the ethmoid bone. In the latter case in no instance does an ascending ramus reach the corresponding descending ramus. This doubtless means a lessened degree of differentiation into ethmoidal conchae in the region of the ascending rami as compared with the corresponding region in ﬁg. 21.
Sometimes there is apparently no attempt at the formation of individual conchae in the region of the ascending rami, hence in these cases the meatuses——with the exception of the meatus medius —do not possess individual ascending rami (ﬁg. 23). In other instances the meatus superior and medius have ascending rami, but the remaining ethmoidal meatuses do not (ﬁg. 25). The ascending ramus of the meatus superior is occasionally so well developed that it reaches nearly to the cribriform plate of the ethmoid bone (ﬁg. 24).
A reference to ﬁgs. 21 to 30 will indicate the irregularity and inconstancy of the ascending rami, With the single exception of the meatus medius. Notwithstanding this inconstancy of the ascending rami, We occasionally have ascending rami as Well marked as the descending rami (ﬁg. 24). Rarely we ﬁnd them all fairly Well marked (ﬁg. 21,), but in the Vast majority of cases the ascending rami of the supreme meatuses Vary from an extremely rudimentary state to a complete absence. The number of times the ascending rami are present in some form, however, justiﬁes the division of the ethmoidal meatuses into ascending and descending portions.
The descending rami. The descending rami of the ethmoidal meatuses are as a rule much better differentiated than are the corresponding ascending rami. What has been said of the ascending rami, z'.e., a gradual change from an oblique to a more or less Vertical plane, as one passes from the meatus medius to the meatus suprema III, applies also, although with less degree, to the descending rami.)
The descending ramus of the meatus medius lies practically in a horizontal plane, and the corresponding ramus of the meatus superior varies from it but little in its general direction (ﬁg. 22). On the other hand, the descending rami of the meatus suprema I, II, and III assume a more vertical direction—the latter being most marked in the meatus suprema III (ﬁg. 21). In very many cases the descending rami of the meatus suprema II and III are extremely rudimentary or not at all differentiated (ﬁg. 29). The descending ramus of the meatus suprema I is present in some form, according to my specimens, in practically all cases. Of course after birth the meatus suprema I in many cases becomes obliterated (62.5 per cent of my adult specimens present a meatus suprema I) and in the adult the concha nasalis superior and suprema I are represented by the concha superior. The meatus medius and superior are, of course, constant in both the fetus and in the adult.
In a general way we may say that the integrity of the ethmoidal meatuses present, with the possible exceptions of the meatus medius and superior, depends practically wholly upon the differentiation and degree of development of the descending rami, and not upon the ascending rarni (ﬁgs. 21 to 24).
The nasal conchae
The concha nasalis inferior. The concha nasalis inferior appears ﬁrst in the formation of nasal conchae, and for some time occupies the greater portion of the lateral nasal wall (ﬁg. 13). It is at ﬁrst not well differentiated, but with the growth of the fold and the deepening of the furrows (meatuses) inferior and superior to it, the concha becomes more sharply outlined. With the growth of the nasal fossa in the dorsal and superior direction, and the resulting development of the ethmoidal region, the concha inferior gradually comes to take on the usual adult form. During the latter stages of intrauterine life it offers nothing of note to justify a further consideration of it in this connection.
The agger nasi. The agger nasi is homologous with the nasoturbinal which is so well developed in some other forms (pig, cow, sheep, dog, skunk, etc.). It is extremely rudimentary in man in comparison, for example, to the corresponding structure in the pig, rabbit, cow, etc. The agger nasi is an elevation located ventral to the concha nasalis media, and ventral and superior to the concha nasalis inferior. It is more or less parallel to the bridge of the nose. It is at times fairly well developed in the late fetus, and again we find it extremely rudimentary (ﬁgs. 22, 25, 29, and 39).
Killian, in conjunction with the processus uncinatus of the ethmoid bone, considers it as an ethmoidal concha, 13.e., belonging to the ethmoidal group of conchae. He considers the processus uncinatus as the descending crus of the agger nasi, and speaks of the two structures as his “erste Hauptmuschel.” In commenting on Killian’s classiﬁcation of the nasoturbinal (agger nasi),Peter, who studied the structure from a comparative point of view, says: “Killian und vor ihm Andere glaubten auch dass das Nasotur— binale in das Schema der Riechmuscheln einzwangen zu miissen und suchten daher nach einem Crus descendens desselben, den sie im Processus uncinatus gefunden zu haben meinten. Nach obiger Darstellung der Muschelentwicklung ist diese Forderung ebenso umberechtigt, wie sie fiir das Maxilloturbinale Wialre.”
I prefer to think of the processus uncinatus as an accessory concha, and to class it with the folds of the bulla ethmoidalis (also accessory conchae of the middle meatus) and with the accessory concha of the superior meatus. While the processus uncinatus is more or less continuous with the agger nasi, and for descriptive purposes might be considered as the descending crus of the agger nasi, it is also in many instances fused ventrally and superiorly with the lateral surface of the concha nasalis media. I have also seen it fused across the infundibulum ethmoidale with the ventral extremity of the bulla ethmoidalis. In subsequent paragraphs I will consider the concha nasalis media as Killian’s “zweite I-Iauptmuschel,” and will not consider the agger nasi and the processus uncinatus as belonging to the regular group of ethmoidal conchae.
The concha nasalis media, superior, suprema I, supreme II, suprema III. The regular group of ethmoidal conchae have many things in common, hence may for the time be considered together. In a general way they all possess knees or bends, thus presenting superior and inferior, or better, ascending and descending portions (Crura ascendens and descendens of Killian). As we pass from the concha media to the concha suprema III, we ﬁnd a gradual lessening in the degree of the knee or bend. The supreme conchae represent practically straight angles, hence no well marked division into ascending and descending crura, 'i.e., the conchae are practically straight. This is also aided in very many cases by the rudimentary development or complete absence of individual ascending crura (ﬁgs. 23 and 29). As we pass from the concha media towards the concha suprema III we ﬁnd a gradual change in the plane of the conchae, from a more or less oblique direction to a more or less vertical one (ﬁgs. 21 and 23).
Explanation of Figures
Figs. 21, 22, 23 (X 1.2) Drawings of specimens of the lateral nasal wall from the anatomical series, Cornell University. The drawings all represent the lateral nasal wall of term fetuses.
Compare especially the regions of the ascending crura of the ethmoidal conchae in the three ﬁgures. In ﬁg. 21 the ascending and the descending rami of the ethmoidal meatuses are continuous. In ﬁg. 22, however, the very rudimentary ascending rami of the ethmoidal meatuses are not continuous with the descending -rami—save in the meatus medius. It will be noticed in ﬁg. 23 that there is no attempt at the differentiation of individual ascending crura for the ethmoidal conchae; the concha media is, however, an exception. In the latter ﬁgure the ascending crura are represented by a general ascending—crural mass undifferentiated.
Note the extensive furrows on the medial surface of the concha nasalis media in figs. 21 and 22.
a,—c_. e, g, 2' = ascending rami of the ethmoidal meatuses; w, u, s, p, n = descending rami of the ethrnoidal meautses; b, d, f, h, k = ascending crura of the ethmoidal conchae; v, t, 1', o, m = descending crura of the ethmoidal conchae; l = sinus sphenoidalis; :1: = Incisura retrolobularis.
FIGS. 24, 25, 26 Drawings of specimens of the lateral wall of the nasal cavity from the anatomical series, Cornell University.
FIG. 24 (X 1.2) From a fetus at term. Shows a marked ascending ramus for the meatus nasi medius. The other ascending rami present are less developed and do not reach the corresponding descending rami. Note also the multiple furrows on the medial surface of the concha. nasalis media.
FIG. 25 (X 1.2) From a 7-months fetus. To show the furrows on the concha nasalis media and the lobule in the region of the knee. There is little or no differentiation in the region of the ascending crura for the concha. superior and the concha suprema I.
FIG. ‘26 (X 1.8) From a 190-day fetus. The differentiation into individual ethmoidal conchae has not progressed very far at this early period. Compare with fig. 21.
The ascending crura. The ascending crura always tend more towards the perpendicular than do the corresponding descending crura. This is especially true of the concha media and superior, also at the times of the concha suprema I (ﬁgs. 21 and 24). Fig. 21 shows ﬁve fairly well marked ascending crura. It will be noticed that they are almost perpendicular to the cribriform plate of the ethmoid bone. However their superior extremities as individual conchae do not closely approach this plate. We may either think of the conchae as fused into one mass, or that differentiation into individual conchae stopped short of the cribriform plate.
FIG. 27 (X 8) Drawing of a frontal section through :the lateral wall of the nasal cavity in the region of the supreme conchae (fetus aged from 7-8 months, series B, slide -48). ’J‘hc concha nasalis inferior is not included in the section.
FIGS. 28, 29, 30 Drawings of specimens of the lateral wall -of the nasal cavity from the anatomical series, Cornell University.
FIG. 28 (X 1.8) From a 190-day fetus. Note especially the rudimentary character nf the concha superior. The accessory concha of the superior meatus cannot be seen.
FIG. 29 (X 1.2) From a 235-day fetus. Note the marked differentiation into descending crura of the ethmoidal conchae. The ascending crural mass is as yet undifferentiated.
FIG. 30 (X 1.2) From a 210-day fetus. Note especially the lobuli on the ethmoidal conchae tendency of the conchae to become straighter as one proceeds from the concha media to the concha suprema III is well illustrated in this ﬁgure (21).
In other cases the individuality of the ascending crura is only faintly indicated by very shallow grooves throwing into slight relief extremely rudimentary crura. In fig. 22 we have such an example. Here we ﬁnd the general ascending-crural mass well developed, but the differentiation into ﬁve ascending crura, with the single exception of the ascending crus of the concha media, only slightly marked. In some instances the ascending crus of the concha media stands out in bold relief. This is especially due to a well developed ascending ramus of the meatus superior (ﬁg. 24). In the latter ﬁgure the ascending ramus of the meatus superior closely approaches the cribriform plate of the ethmoid bone.
Occasionally the whole ascending-crural mass presents an even and unbroken surface, there being no furrows or grooves to throw any portion of the mass into relief. In such instances there is no differentiation of the mass into individual ascending crura; however we may consider this mass as representing the ascending crura undifferentiated (ﬁg. 23). If not the latter, then we must say that the individual ascending crura coalesced into a general fold or mass at an earlier stage. The former theory is, however, the most plausible according to my observations. The general ascending-crural mass is ‘often more or less overhanging in character. Again we may have the ascending crura of the concha media and superior well outlined, while the supreme group (I, II, III) is represented by one fold (ﬁg. 29).
A reference to ﬁgs. 21 to 30 will show some of the different combinations met with in the fetal specimens examined for the substance of this paper.
The descending crura. The descending crura of the ethmoidal conchae are, almost without exception, better differentiated than are the corresponding ascending crura. The former also occupy a more nearly horizontal plane; this, however, lessens as we approachthe concha suprema III. The middle and superior conchae present the best marked descending crura. The concha suprema I also frequently possesses a well marked descending crus. The descending crura of the conchae supremae II and III, are variable and frequently entirely wanting. At times the latter two are fused into one, and then in turn closely associated with the anterior surface of the body of the sphenoid bone, in the region of the developing sinus sphenoidalis. The concha suprema III loses its identity early by becoming associated with the anterior surface of the body of the sphenoid bone.
Lobules and nodules of the ethmoidal conchae. At’ the junction of the ascending and descending crura, or in the region of the knees, we frequently ﬁnd overhanging lobule formations. This is a fairly constant condition for the concha media, and it is also very common for the concha superior (ﬁgs. 2] and 28). Occasionally the concha suprema I also presents a similar formation, which in some cases more or less overhangs the supreme meatuses and conchae. In the latter case it really amounts to the ascending crura of the supreme conchae (ﬁg. 30). Schwalbe in his “Anatomic der Sinnesorgane,” refers to the lobule of the concha nasalis media as the ‘Operculum meatus narium medii.’ He does not, however, refer to similar formations of some of the other conchae. Frequently there is a secondary thickening on the middle of the lobules. Zuckerkandl calls attention to this for the lobule of the concha media; however the other lobules frequently present the same condition (ﬁgs. 25 and 30). Killian refers to this secondary prominence as the ‘N odulus lobuli.’ Fig. 30 shows three well formed lobules—the superior one more or less operculating the conchae and the meatuses in the immediate vicinity. The lobule of the concha media is at times very prominent, and it takes on different shapes as is evidenced by ﬁgs. 21 and 25.
My studies have led me to agree with the statement of Peter, namely, that “Dieser Lobulus mit Nodulus ist der Vorderen Spitze der Ethmoturbinalia der Saugetiere zu vergleichen.”
Grooves on the concha nasalis media. The concha nasalis media needs further consideration separately, since it presents grooves or furrows on its medial and inferior surfaces (ﬁgs. 22, 23, and 25). These furrows which show on the mucous membrane covering the concha, generally present corresponding depressions in the conchal cartilage or bone. At times we ﬁnd marked furrows on the conchal cartilage yet the surface remains unfurrowed in these positions. Killian concludes, therefore, that “der Knorpel scheint dernnach weit conservativer in der Bewahrung der urspriinglichen Form zu sein, als die SchleiInhaut.” The two most constant of these furrows according to my specimens are what may be termed, (1) the superior and (2) the inferior (ﬁg. 25). In ﬁg. 22 we have an extensively developed superior furrow. It more or less splits the descending crus of the concha media into superior and inferior portions. The latter condition led some former investigators (Zuckerkandl and others) erroneously to consider the deep furrow as one of the chief ethmoidal furrows, and the portion of the concha media superior to-the furrow, as a separate ethmoidal concha (mittlere Siebbeinmuschel, Zuckerkandl). Seydel later showed the error of this contention, and Zuckerkandl subsequently retracts from his former view in the following words: “Dagegen mochte ich das Gleiche fiir die untere Siebbeinmuschel nicht mehr aufrecht erhalten, denn wir haben erfahren, dass die mittlere Siebbeinmuschel nicht nur_ aus einer Teilung der Concha ethmoidalis inferior hervorgeht. und stimme O. Seydel bei, der die untere Siebbeinmuschel als Reprasentantin eines einzigen Riechwulstes ansieht.”
Killian refers to the furrows of the concha media as ‘Nebenfurchen,’ and the notch formed by the inferior furrow differentiating to the free inferior border of the concha media, dorsal to the lobule of the knee, as the ‘Incisura retrolobularis’ (ﬁg. 21). Sometimes the superior furrow is broken into three or more grooves, rather obliquely placed, the ventral one being as a rule the best marked (ﬁg. 24).
Accessory nasal folds (conchae) and furrows
Upon turning superiorly the concha nasalis media of the adult nose we expose for study the bulla ethmoidalis and the processus uncinatus——accessory conchae of the meatus nasi medius. By removing the concha nasalis superior we also expose in very many cases an accessory fold or concha on the lateral wall of the meatus nasi superior which is comparable to the bulla ethmoidalis. These structures contained in the middle and the superior meatuses are hidden or accessory nasal conchae, comparable to the accessory conchae found in mammals. In the middle meatus we also note the hiatus semilunaris, and if the processus uncinatus be turned inferiorly, the infundibulum ethmoidale is exposed. In the superior and ventral portion of the middle meatus we note Varyi.ng relations in different specimens, between the nasofrontal duct and the infundibulum ethmoidale and some of the anterior ethmoidal cells. The ostia of ethmoid cells are also to be seen in the meatus medius, superior, and suprema I———the relations of these ostia varying much in different specimens.
In order to interpret these varying adult conditions and relations, it is essential that we study the developmental changes in the middle and the superior meatuses at some length in the embryo, late fetus, and in the young child. This will at once point out the probabilities of development and the varying adult conditions one may expect to meet in a series of specimens.
The accessory folds and furrows of the descending ramus of‘ the meatus hast’ medius. If we examine serial frontal sections of the nose of a 40-day embryo we will ﬁnd that the lateral" wall of the meatus, nasi medius is more or less even and simple. If, on the other hand, we examine the same region in embryos aged from 50 to 60 days we will ﬁnd a somewhat crescentic shaped fold with its free border directed superiorly, breaking the evenness of the wall. The latter is the anlage of the processus uncinatus and the ﬁrst of the series of accessory folds to appear on the lateral wall of the meatus medius. This fold at once aids in forming a furrow immediately superior to it—the primitive infundibulum ethmoidale. It is quite probable that the furrow ﬁrst establishes an anlage and this in turn throws into slight relief a portion of the mucous membrane inferior to it, thus establishing the anlage of the processus uncinatus. It may, however, be said that both structures are more or less dependent upon each other in establishing anlages. The same principles are obviously here involved just as they are in forming the primitive nasal meatuses and conchae.
From this furrow (primitive infundibulum ethmoidale) the sinus maxillaris develops its anlage in the form of an evag'ination of the mucous membrane. This maxillary sinus anlage begins to be established from the sixty-ﬁfth to the seventieth day of embryonal life. In a former paper I suggested that primitively the pouching of the sinus maxillaris aided in deepening the infundibulum ethmoidale; thus causing the processus uncinatus to stand out better at an early period.
Shortly after this we have the first evidence of the bulla ethmoidalis, appearing superior and lateral to the processus uncinatus. The bulla ethmoidalis is ﬁrst indicated by special thickenings (one or two) of the lateral plate of cartilage——the cartilaginous thickenings appearing on its medial surface. At ﬁrst the bullar anlages do not cause the mucous membrane to bulge towards the lumen of the nasal cavity; hence these early stages pass unobserved unless one examine serial frontal sections through this region. Later, however, say in a 120-day embryo, the cartilaginous prominences have developed sufficiently to push the mucous membrane on the lateral wall of the meatus medius into relief (ﬁgs. 17 and 18). We now have established a fold, or folds, (bullar folds) lateral and superior to the processus uncinatus. If two folds appear there is an intervening furrow. These folds represent the primitive bulla ethmoidalis. Usually the intervening furrow, when present, disappears after birth. Occasionally, however, an ethmoidal cell develops from this furrow.
Thus far no mention has been made of another fold that appears in many cases inferior to the bullar folds and lateral to the infundibulum ethmoidale. Because of its relations to the infundibulum ethmoidale I shall speak of this as the infundibular fold. It is never very prominent and forms in part the lateral wall of the infundibulum ethmoidale. It may persist as a fold after birth, but it generally becomes leveled down to an even surface which imperceptibly passes on to the bullar surface.
It will, therefore, be seen that we have, during the latter half of intrauterine life, fairly well outlined grooves and folds on the lateral wall of the descending ramus of the meatus medius. If we take into consideration the extreme cases found in the late fetus we have thus formed four folds and four furrows. These folds may appropriately be named superior and inferior bullar folds, infundibular fold, and processus uncinatus; the furrows, the suprabullar -furrow or recess, the bullar furrow, the infrabullar furrow, and the infundibulum ethmoidale. The suprabullar recess and the infundibulum ethmoidale are constant and are the most important furrows. The others are of less importance and are more irregular and inconstant in their development (ﬁgs. 31 and 34).
Killian, who has studied this region extensively, ﬁnds a similar number of folds and furrows on thelateral wall of the middle meatus. He, however, considers the processus uncinatus as the descending crus of his ‘erste Hauptmuschel,’ hence includes it in the class of regular ethmoidal conchae. My superior bullar, inferior bullar, and infundibular folds or conchae correspond to his ‘obere, mittlere, und untere N-ebenmuscheln,’ respectively. My suprabullar, bullar, and infrabullar furrows, and infundibulum ethmoidale correspond to his ‘Recessus superior, obere Zwischenfurche, untere Zwischenfurche, und Recessus inferior,’ respectively.
The suprabullar furrow or recess. The suprabullar furrow or recess is practically constant. It varies somewhat in its form and extent, but all specimens give some evidence of it. At times it continues ventrally and superiorly almost to the cribri-form plate of the ethmoid bone (ﬁg. 38); however, in the majority of cases it does not extend so far, due to partial fusion between the superior border of the superior bullar fold and the attached border of the concha media (ﬁg. 41). It is frequently also limited inferiorly and dorsally by similar fusion. Again, there may be multiple points of fusion between the superior bullar fold and the concha media, thus breaking the suprabullar recess or furrow into several compartments (ﬁg. 43). The recess in many cases early tends to deepen or pouch laterally and inferiorly behind the bullar folds (ﬁg. 35). In this manner the bulla becomes more or less shell-like in structure; and some of the so—called bullar cells are thus established. The suprabullar recess is a constant point from which anterior ethmoidal cells develop (ﬁgs. 31, 34, and 43).
The bullar furrow. The bullar furrow is placed between the two bullar folds or accessory conchae (ﬁg. 31). It is variable in its differentiation and not at all constant. It is generally obliterated by the superior and the inferior bullar folds becoming continuous structures in the formation of the adult bulla ethmoidalis. This coalescence is, however, not always absolute, in that an ethmoidal cell may develop from the furrow, leaving the ostium of the adult cell at the point of the primitive furrow (ﬁgs. 31 and 39). Even in many adult specimens we ﬁnd evidences of this primitive furrow in the form of a shallow groove on the medial surface of the bulla ethmoidalis. An ethmoidal-cell ostium on the medial surface of the bulla ethmoidalis is almost invariably the remains of the early bullar furrow.
The infrabullar furrow. The infrabullar furrow is placed between the inferior bullar and the infundibular folds (ﬁg. 31). It is very inconstant and when present is frequently obliterated by the inferior surface of the bulla ethmoidalis becoming continuous with the infundibular fold. In some cases it is fairly well marked (ﬁg. 34) but, as a rule, it is of minor importance. Rarely an ethmoid cell develops from the furrow—the adult cell draining into the infundibulum ethmoidale.
The inftmdibulum ethmoidale. The infundibulum ethmoidale (Recessus inferior der absteigenden Schenkel der ersten Hauptfurche of Killian) is invariably present in some form. It is formed early, and obviously aids in establishing the primitive processus uncinatus. It is directed somewhat ventrosuperiorly and at its ventral and superior termination it may end blindly or develop into an anterior ethmoid cell. At other times it is variously continued into one of the frontal furrows. Rarely it continues its development ventrally and superiorly, remaining lateral to the frontal furrows, and in this way may establish the frontal sinus (ﬁgs. 36, 37, 39, and 40).
Dorsally and inferiorly it either gradually loses its depth and thus becomes continuous with the middle meatus, or it ends rather abruptly in a pocket, due to the superior and lateral curving of the dorsal end of the processus uncinatus at this point (ﬁg. 49). From the infundibulum ethmoidale the sinus maxillaris develops, hence in the adult the latter sinus communicates with the infundibulum ethrnoidale, and only indirectly Via the hiatus semilunaris with the meatus nasi medius (ﬁg. 18).
FIG. 31 (X 3.9) Drawing of a. frontal section of the left nasal fossa of a term fetus (series D, slide 5).
Note the individual folds comprising the bulla ethmoidalis, and the fold lateral to the infundibulum ethmoidale, and the furrows that border these folds. The cell that is indicated in the superior bullar fold is an extension from the suprabullar furrow, and the cell indicated in the concha media communicates a few sections farther dorsally with the meatus nasi medius (compare with fig. 35).
The superior bulla?‘ fold or concha. The superior bullar fold or concha is located immediately inferior to the suprabullar recess (ﬁg. 31). It may continue independently ventrally and superiorly almost to the cribriform plate of the ethmoid bone. In other cases it may be fused at certain points with the attached border of the concha nasalis media (figs. 41 and 43). It is frequently continuous with one or more frontal folds (ﬁg. 41). It usually comes to form the chief bulk of the adult bulla ethmoidalis.
In many cases there is no differentiation ‘into superior and inferior bullar folds by an intervening -furrow——thfe bullar furrow. The inferior bullar fold or concha. The inferior bullar fold or concha is, as stated above, not always differentiated from the superior bullar fold. It is, however, occasionally well isolated and stands more or less as an independent fold (ﬁgs. 34 and 39).
FIGS. 32 and 33 Photomicrographs of frontal sections through the right nasal fossa of a 7-months fetus (series B slide 31), Section ﬁg. 32 is through the ventral portion, and section ﬁg. 33 is through the dorsal portion of the fossa.
The frontal furrows have pouched towards the frontal region in the establishment of early anterior ethmoid cells (ﬁg. 32).
See page 662 for explanation of lettering.
The latter condition is especially marked in the cases where an anterior ethmoid cell develops from the bullar furrow (ﬁg. 39). I agree with Killian that the superior and inferior bullar folds (obere und mittlere Nebenmuscheln, Killian) usually coalesce to form the adult bulla ethmoidalis. Sometimes, even in the adult, we see evidences of the primitive bullar furrow, which more or less grooves the medial surface of the adult bulla. In many instances coalescence is, however, not necessary because there was at no time a differentiation into two portions.
FIG. 34 and 35 Photomierographs of frontal sections through the left nasal fossa in the region of the bullar folds, from a term fetus (series D, slides 5 and 6). Note the bullar folds, the cells in the concha media, and the superior bullar fold in ﬁg. 34. In fig. 35, which is a section farther dorsal, the ostia of the cells are shown, It shows how the suprabullar furrow or recess tends to develop or pouch behind and lateral to the hullar folds; this in time causes the bulla to become shell like.
F. furrows, = frontal furrows; cc. eth. ant, = cellulae ethmoidales anterior; Inf. eth., = infundibulum ethmoirlale; D. nasul., =ductus nasolacri1nalis;S. mam, = sinus maxil1aris;Sbr., = su prabullar recess or furrow; Cc. eth., = cellulae ethmoidales; S. m., = sinus maxillaris; Con. nas. mecl., = concha nasalis media.
The infundibular fold or concha. The infundibular fold is very rudimentary and more or less ineonstant. It is located lateral to the infundibulum ethmoidale and in part forms its lateral wall (ﬁg. 35). It is more or less separated from the inferior bullar fold by the shallow infrabullar furrow. It usually loses its identity in the adult, in that it imperceptibly passes to the bullar surface by the obliteration of the infrabullar furrow. Occasionally it is well marked and is more or less isolated from the inferior bullar fold by a relatively deep infrabullar furrow. Rarely it retains its identity in the adult—this is especially so when an anterior ethmoidal cell develops from the infrabullar furrow.
FIG. 36 (X 8) Drawings of frontal sections through a. portion of the lateral nasal wall of a 7-months fetus, in the region of the frontal recess (series C, slide 5). Section A is farther ventral than is section B. Note the blind ventral extremities of the frontal furrows in section A which, at this plane of section, are in reality early anterior ethmoidal cells. Any one of these cells may develop into a frontal sinus, or two may develop sufficiently far
to be called frontal sinuses. The frontal recess may also develop into the frontal sinus.
In section B some of the furrows communicate freely with the frontal recess, and at this plane of section are more truly frontal furrows.
The processus uncinatus. The processus uncinatus is a constant structure, and is medial and inferior to the infundibulum ethmoidale. As was stated before, it is the ﬁrst of the accessory or hidden conchaeto be differentiated. At its ventral and superior end it terminates in various ways. In some cases it is continuous with one or more frontal folds and at the same time its base continued on to the agger nasi (ﬁg. 41). In other instances it is fused with the lateral surface of the concha media at its ventral
FIG. 37 (X 5) Drawing of a frontal section through the left nasal fossa of a fetus aged approxirnately7months (series B, slide 31). The section is in the region of the frontal recess.
Note the frontal folds (accessory conehae) and the frontal furrows. SOIIIO of the furrows, either by coalescence of the folds or by the extension of the furrows towards the frontal region, end blindly and represent early anterior ethmoitl cells. The frontal recess is really obliterated by the coalescence of some of the frontal folds with the lateral surface of the conch-a nasalis me(lia—co1npare this condition with that found in fig. 36 B. extremity, or even fused with the ventral extremity of the bullar folds. Ventrally and inferiorly the base of the processus uncinatus becomes continuous with the surface of the agger nasi. Some observers class the processus uncinatus with the general ethmoidal conchae.
The accessory folds and furrows of the ascending mmus of the meatus nasi medius, z'.e., of the recessus frontalis. In a previous paragraph mention was made of the rather early beginning of an extension of the meatus nasi medius from its ventral and superior part. This extension of the middle mcatus towards the frontal region is the ﬁrst step in the formation of the frontal sinus and certain of the anterior ethmoid cells. To this extension or recess Killian has given the appropriate name, ‘Recessus frontalis.’ For some time the lateral wall of this recess (ascending ramus of the middle meatus) is even and unbroken. If we examine frontal and horizontal sections of the recess of a 4-months fetus we will ﬁnd the lateral plate of cartilage thickened at certain points, in the form of projections directed towards the lumen of the nasal fossa. For some time this condition prevails and the mucous membrane is not at first thrown into relief. These thickenings, which I ﬁnd vary in number, are in anticipation of the folds (accessory conchae) which are present on the lateral wall of the frontal recess of a later fetus.
The folds as found in the late fetus are variable in number and as a rule are not very prominent. Their prominence depends largely upon the degree of development of the intervening furrows or pits. The folds as a rule more or less lose their identity after birth, and the furrows orpits variously remain as ostia of anterior ethmoid cells. The folds have been appropriately termed frontal folds or conchae, and the bordering furrows or pits, frontal furrows.
The frontal folds and furrows vary in degree of development and differentiation. We frequently ﬁnd specimens with four Well formed furrows and three resulting folds (ﬁg. 41). In other cases, either by earlier coalescence or, I think better, by alessened degree of differentiation, we have a smaller number of folds and furrows (ﬁg. 40). In ﬁg. 41 it will be noticed that the processus uncinatus is continuous with the ﬁrst and second frontal folds. The processus uncinatus in the latter case also sends a fork towards the agger nasi, and gains slight fusion with the lateral surface of the concha nasalis media. The superior bullar fold is in part directly continuous with what might be termed the third frontal fold. In ﬁg. 38 we ﬁnd that the processus uncinatus is continued ventrally and superiorly to the agger nasi; in part fusing with the concha nasalis media at this point. The superior and inferior bullar folds in the latter instance are continued superiorly" to become continuous with the ﬁrst and second frontal folds. Note that the third frontal furrow is more or less continuous with the suprab'ullar recess, and that the latter recess continues almost to the cribriform plate of the ethmoid bone. The infundibulum ethmoidale continues ventrally and superiorly into a frontal furrow. Compare this condition of the infundibulum ethmoidale with that found in figs. 39 and 41.
In ﬁg. 40 there is only one frontal fold or concha differentiated. The concha is bordered by two frontal furrows, and the infundibulum ethmoidale is continued ventrally and superiorly into these furrows. In ﬁg. 39 the processus uncinatus is continued ventrally on the lateral wall of the frontal recess and apparently the frontal folds extend from it. In the latter ﬁgure note also the relations of the infundibulum ethmoidale in the region of the frontal recess, and the superior and inferior bullar folds and the infundibular fold.
At times the frontal folds or conchae fuse with the lateral surface of the concha nasalis media and in this manner we have the obliteration of the frontal recess. .In such cases the sinus frontalis must develop from an anterior ethmoid cell, and not by direct extension of the frontal recess (ﬁg. 44). In ﬁg. 36 the frontal folds have not fused with the lateral surface of the concha nasalis media and, therefore, the frontal recess is maintained. In such a condition the sinus frontalis may develop either from the frontal recess or from one or more anterior ethmoid cells. It is difficult to say in the latter ﬁgure whether the frontal folds or conchae have coalesced with one another, thus constricting off small blind pouches (early anterior ethmoid cells), or whether the frontal furrows in anticipation of anterior ethmoid cells have pouched toward the frontal region, thus closely simulating coalescence between the several frontal folds, but making coalescence only apparent rather than real.
A comparison of ﬁgs. 36 to 42 (showing both frontal sections and surface views of the frontal recess and the descending ramus of the meatus medius) will materially aid in clearing up the Various adult conditions one meets in these regions, in connection with the gross anatomy and relations of the nasofrontal duct, the infundibulum ethmoidale, and the bulla ethmoidalis.
The accessory fold or concha of the mcatus nasi superior. At this juncture mention must again be made of a rather frequent accessory concha that is differentiated rather early on the lateral wall of the descending ramus of the meatus nasi superior (fig. 45). Seydel directs attention to it in the following words: “Bei menschlichen Embryonen fand ich einige Male in dem Spalt zwischen der mittleren und obern Muschel, also an der Stelle, wo bei den Halbaffen die zweite Nebenmuschel liegt, eine niedrige leistenformige Erhebung der seitlichen Nasenwand Ich mochte diese Bildung als Rest der Nebenmuschel deuten.”
The anlage of this accessory concha is indicated rather early, and by the fourth month of fetal life it is well established (fig. 19). Killian considers this fold important as a point for orientation: “Die Nebenmuschel im Bereiche der zweiten Hauptfurche ist, Wenn nachweisbar, ein vorziigliches Orientirungsmittel namentlich zur Bestimmung des Crus descendens 3,” z'.e., the crus descendens of my concha nasalis superior. Some earlier Writers thought that the concha superior developed or became differentiated from the concha media—this because of the furrow that is very frequently found on the medial surface of the descending crus of the concha media in the fetus (fig. 22). Seydel later pointed out the error of this contention, and Zuckerkandl agreed that he previously was in error in saying that the ‘mittlere Siebbeinmuschel’ (concha superior) was differentiated from the ‘untere Siebbeinmuschel’ (concha media). Zuckerkandl then advances the theory “dass die mittlere Siebbeinmuschel nicht nur aus einer Teilung der Concha ethmoidalis inferior hervorgeht, sondern iiber derselben und unabhangig von ihr sich entwickelt und als Rudiment in der unteren Siebbeinspalte steckend angetroffen wird.” It appears that Zuckerkandl in speaking of the Variations of the ‘mittlere Siebbeinmuschel,’ at times mistakes the accessory concha of the superior meatus for his ‘mittlere Siebbeinmuschel’ (concha nasalis superior). What he designates as the ‘Anlage der mittleren Siebbeinmuschel,’ (Tafel VII, Fig. XI, Rormale und pathologische Anatomie der Nasenhohle und ihrer pneumatischen Anhange, Bd. I, Wien und Leipzig, 1893) certainly corresponds to my accessory concha of the superior meatus, and not to my concha nasalis superior.
In case the accessory concha of the superior meatus is well developed we have fairly well formed superior and inferior recesses. The inferior recess is especially deep in the cases Where the ‘crista suprema’ of Killian is Well developed (ﬁg. 45). This condition makes the superior meatus look much like the middle meatus, i.e., the accessory concha of the superior meatus takes the place of the bulla ethmoidalis (accessory concha of the middle meatus), and the ‘crista suprema’ takes the place of the processus uncinatus (compare ﬁgs. 18 and 45).
The inferior recess of the superior meatus may continue superiorly and ventrally into the blind superior termination of the superior meatus. The accessory concha is, however, at times wholly or in part coalesced with the concha media, thus obliterating wholly or partly the inferior recess. Frequently a posterior ethmoidal cell develops from the inferior recess. The superior recess is often obliterated by coalescence between the accessory concha and the concha superior. In other instances the superior recess may be continued ventrally and superiorly to the blind end of the meatus superior. Occasionally an ethmoid cell develops from this recess.
4. The Anlages of the Sinus Paranasales
After the preceding consideration of the meatus nasi and the conchae nasales, and the accessory folds and furrows, the genesis of the sinus paranasales becomes Inuch simpliﬁed and fairly easy of interpretation. That all of the paranasal chambers develop from preformed or preexisting furrows is certainly in accord with my observations. Since the paranasal or accessory cavities develop from preformed furrows and recesses, it is difficult to say just when they begin to establish anlages. I, however, believe that anlages are established much earlier than is generally supposed~in fact the furrows and recesses from which the paranasal sinuses develop are in a sense the ‘primitive’ anlages of these chambers. The early tendency for the sinuses to establish their ‘ﬁrst’ anlages may be no mean factor in making the recesses and furrows what they early are.
The preexisting spaces from which paranasal air chambers may develop, according to my studies, are: (1) the suprabullar recess, (2) the bullar furrow, (3) the infrabullar furrow, (4) the infundibulum ethmoidale, of the descending ramus of the meatus nasi medius; (5) the frontal furrows, (6) the frontal recess, of the ascending ramus of the meatus nasi medius; (7) the ventral and superior extremity of the meatus nasi superior; (8) the recessus superior, (9) the recessus inferior, of the meatus nasi superior; (10) the meatus nasi suprema I.
Of the above named spaces we rarely ﬁnd air cells developing from the infrabullar furrow, and only occasionally from the bullar furrow. I, however, ﬁnd that rather 'frequently posterior ethmoid cells develop from the inferior and superior recesses of the meatus nasi superior, and about 75 per cent of specimens in which the meatus suprema I persists we ﬁnd a posterior ethmoidal cell developing from the latter meatus (the meatus nasi suprema I is present in about 62.5 per cent of adult specimens). I ﬁnd that the remainder of the aforementioned spaces are quite constant in cell development. We must, however, remember that the development of cells from the frontal furrows and recess is very variable.
Because the anlages of the paranasal chambers have primitively different relations, Killian divides them thus:
- solche, die zwischen je zwei Hauptmuscheln (I. Ordnung);
- solche, die zwischen einer Haupt— und einer Nebenmuschel (II. Ordnung) und
- solche, die zwischen je zwei Nebenmuscheln gelegen sind (III. Ordnung).”
Varying views have been advanced by different writers as to the genesis of the paranasal chambers. Dursy thought that the establishment of all the accessory air spaces of the nose, with the exception of the anlages of the maxillary and sphenoidal sinuses, was wholly dependent upon resorptive processes taking place in the cartilaginous and bony framework of the nose. This is certainly not the earliest factor involved in the establishment of anlages. Others, who worked this region in some of the lower forms, considered the space included by the lateral curling of some of the conchae as ethmoidal cells——a View that is not tenable. Seydel in a subsequent paper, comes nearer the truth when he writes: “ .ihre Entwicklung von den Spalten zwischen je zwei (auch rudimentaren) Muscheln ausgeht.”
Killian in ’96, in an exhaustive paper, places to my mind the genesis of the paranasal chambers on a sound basis. My observations in the main agree with his. Whether, as KilIian’s schemata suggest, coalescence takes place between neighboring folds and conchae, thus constricting off a portion of the respective furrow to become the anlage of a cell, seems to me a difficult problem to solve. I rather hold that the nasal mucous membrane in the position of the furrow pouches in the direction of a future cellthis closely simulating coalescence of neighboring accessory folds, or an accessory fold and a concha at these points There seems to be an inherent tendency for the nasal cavity early to enlarge its surface area by the formation of furrows, folds, and pouches. I t indeed seems difficult to decide whether, for example, in ﬁgs. 36 and 44, the frontal folds or conchae coalesced with each other, thus forming blindly ending furrows, or whether the frontal furrows pouched in the frontal direction, thus simulating coalescence but making it only apparent rather than real. It, however, matters very little what interpretation We place here~— probably both factors are more or less involved—the fact remains that from these preexisting furrows and recesses the accessory air spaces develop. This is true of all the paranasal chambers with the single exception of the sphenoidal sinus, which is at ﬁrst, as former writers have pointed out, nothing but a constriction from the dorsal and superior portion of the nasal fossa. Of course the factors of growth ( of the sac) and resorption (of surrounding tissue) are early brought into play (ﬁg. 20).
Explanation of Figures
Fios. 38, 39, 40 Drawings from dissections of specimens from the anatomical series, Cornell University The dissections have been made with special reference to the furrows and folds on the lateral surface of the frontal recess, and the bullar folds on the lateral wall of the descending ramus of the rneatus medius. The specimens are from term fetuses.
FIG. 38 (X 1.8) The concha media has been partly cut away so as to expose the frontal recess and its structures and the bullar folds and furrows. The processus uncinatus has also been partly cut away so as to get a better exposure of the bullar folds and the primitive sinus maxillaris.
FIG. 39 (X 1.2) The concha media has been partly cut away thus securing a good exposure of the frontal recess with its folds and furrows, and the folds and furrows of the bulla ethmoidalis. The infundibular fold is also well shown in the drawing.
FIG. 40 (X 1.2) Especially note the frontal recess and the low degree of differentiation of frontal folds as compared with the specimens represented in figs. 38 and 39. The processus uncinatus is too large to allow the inferior bullar fold to be seen. Portions of the concha media and superior have been cut away.
Ems. 41, 42, 43 Drawings from dissections of specimens from the anatomical series, Cornell University. The dissections have been made with especial reference to the ascending and descending rami of the meatus medius. The concha media is partly cut away in all the specimens.
FIG. 41 (X 1.2) Shows the well formed frontal folds (conchae) and furrows on the lateral wall of the frontal recess, also the accessory concha of the meatus superior. From a term fetus.
FIG. 42 (X 1.2) Note the manner of pouching of the frontal furrows and the frontal recess in the formation of anterior ethmoidal cells and the frontal sinus; also the developing sinus sphenoidalis. This specimen was from a child aged approximately five months.
FIG. 43 (X .6) In this specimen there were apparently no frontal folds nor furrows, or they were early obliterated. It will be noticed that the frontal recess is expanding towards the frontal region in the establishment of the frontal sinus. Note also the multiple ethmoid-cell anlages in the region of the suprabullar furrow. From :1 child aged approximately fourteen months.
The sinus maxillaris
The sinus maxillaris is primitively merely a pouching or evagination of the mucous membrane of the infundibulum ethmoidale. This pouching is very evident about the seventieth day of fetal life, and is best shown by reconstructing the infundibulum ethmoidale. The earliest changes in its anlage-formation are so slight that they are difficult of appreciation by an examination of serial sections only. The anlage of the sinus maxillaris is usually represented by a single pouch, but, as I stated in a previous paper, we sometimes ﬁnd two pouches growing side by side from the infundibulum ethmoidale. Again the pouching may be very extensive, and in these cases it is indeed hard to say Where the infundibulum ethmoidale ends and where the anlage of the sinus maxillaris begins. In such cases the infundibulum ethmoidale is in a sense a part of the sinus maxillaris. Seydel makes the general statement that “der Raum des Infundibulum, der zwischen Processus uncinatus und Orbitalwand liegt, ist als ein Theil des Sinus (sinus maxillaris) zu beurtheilen.” If we accept the above interpretation then the sinus-maxillaris anlage is established with the ﬁrst evidences of the infundibulum ethmoidale. Zuckerkandl also, presumably, considers the infundibulum ethmoidale a part of the early sinus maxillaris. What he labels “S.m.” (Sinus maxillaris), (Tafel XI, Figs. 5, 6, Normale und pathologische Anatomie der Nasenhohle und ihrer pneumatischen Anhange, Ed. I, Wien und Leipzig, 1893) is certainly in part infundibulum ethmoidale. We seldom see the primitive sinus maxillaris so far ventral as Zuckerkandl represents it to be in Fig. 6, Taf. XI, of the above named work. What he labels “S. m.” in the latter ﬁgure is, I think, wholly infundibulum ethmoidale, z'.e., a frontal section of the superior and ventral portion of it. I, however, think that we should speak of the sinus maxillaris as developing from the preexisting furrow (infundibulum ethmoidale), and not consider the latter a part of the sinus maxillaris. However, as stated before, it is difficult at times to draw this distinction; especially so when the primitive sinus maxillaris is extensive and occupies the greater portion of the infundibulum ethmoidale in its early pouching.
The duplication of the primitive maxillary pouch, and the extensive pouching that we occasionally have, is entirely in accord with adult conditions—~—in that the adult ostium maxillare varies from a small aperture to a long slit-like opening, while in other cases the ostium is duplicated. In this connection I may be permitted to quote brieﬂy from an earlier paper: “I have found the primitive maxillary pouch duplicated . . . This may explain some of the duplications of the ostium maxillare of the adult sinus. The two primary pouches may fuse distally, leaving the two points of evagination as the ostia maxillaria of the adult cavity. -This embryonal condition in all probability explains some of the cases in which the sinus maxillaris is divided into two partly or wholly separate compartments by a vertical partition, '£.e., each pouch developing into -an adult cavity independent of its mate . . . . The great differences in the dimensions of the adult ostium may be due to the coalescence of two or more maxillary pouches; or the primitive pouching may have been single but extensive.”
The early sinus maxillaris is for a time a slit-like cavity in the lateral wall of the nose. It extends inferiorly into the recess formed by the union of the cartilage of the lateral wall with that of the concha nasalis inferior (ﬁg. 18). By resorption (of cartilage) and growth (of the" sac), the sinus ultimately breaks through the cartilage in the position mentioned above (ﬁgs. 31 and 34). Its further extension into the body of the maxilla is accomplished by the simultaneous growth of the sinus and the resorption of surrounding bone, this taking place pari passu with the growth of the face.
For a further consideration of the sinus maxillaris the reader is referred to a previous paper bearing directly upon this cavity.
The sinus frontalis
The point from which the sinus frontalis develops is somewhat variable. Like the sinus maxillaris it develops from a preformed cavity or space. In a previous paragraph mention was made of the frontal recess, and of the folds and furrows which conﬁgure its lateral wall. The recess and the furrows especially concern us in connection with the development of the sinus frontalis. It will be recalled that the number of furrows is variable, and that the infundibulum ethmoidale bears inconstant relations to these furrows (ﬁgs. 38 to 43). At term, or even somewhat earlier, the furrows have already pouched at their superior ends towards the frontal region, thus forming early anterior ethmoidal cells. Frontal and horizontal sections will, therefore, if made at appropriate planes, show cross-sections of cavities instead of furrows (compare ﬁgs. 36, 44, and 32). The frontal recess is at this time also quite roomy and is more or less variable in its extent (ﬁgs. 36 and 41).
As Killian has properly pointed out, the frontal sinus may develop from one or more anterior ethmoid cells, from an ethmoid cell and the frontal recess, or by direct extension of the whole frontal recess. At birth it can hardly be said from what point the frontal sinus will ultimately develop into the adult cavity. According to my studies the frontal sinus may also in exceptional cases develop from the superior and ventral end of the infundibulum ethmoidale, '£.e., the infundibulum ethmoidale continuing its development superiorly and ventrally, lateral to the frontal. recess and frontal furrows, and then expanding into the sinus frontalis. In the vast majority of cases, however, the infundibulum ethmoidale has absolutely nothing to do with the development of the frontal sinus. Lateral Wall of the Cavum Nasi in Man. 677
Does the embryology account for the varying adult relations of the nasofrontal duct and the sinus frontalis, with the structures in the ventral and superior portion of the meatus nasi medius? To this question I must give an affirmative answer, because I think that careful analyses of this region in a series of adult specimens justiﬁes our embryological conclusions.
FIG. 44 (X 3.9) Drawing of a frontal section through the nose of a term fetus (series D, slide 4). The frontal furrows have pouched towards the frontal region and have established early anterior ethmoid cells. The frontal recess is obliterated by the coalescence of the frontal folds with the lateral surface of the concha nasalis media—compare with fig. 36 B.
It will doubtless aid in making the adult conditions one meets more comprehensible if we here refer to speciﬁc fetal conditions. In ﬁg. 41 the infundibulum ethmoidale is in line with the third frontal furrow, but not directly continuous-with it. If in this case the frontal sinus should develop from the anterior ethmoid cell of the ﬁrst or second frontal furrows, or from the frontal recess directly, the nasofrontal duct of the adult sinus would doubtless communicate directly with the meatus nasi medius and not with the infundibulum ethmoidale. If, on the other hand, the frontal sinus should develop from the cell of the third frontal furrow, the nasofrontal duct would practically be continued down to the infundibulum ethmoidale, but not directly continuous with it, unless the bridge of intervening tissue were resorbed as it frequently is. A frontal sinus developing from the cell of the third frontal furrow would in all probability have a tortuous nasofrontal duct, this of course depending largely on the disposition of the other anterior ethmoid cells.
In the specimen shown in ﬁg. 38 the infundibulum ethmoidale and the first frontal furrow are practically continuous with each other.‘ Should the frontal sinus develop from the first frontal furrow in such a condition, the nasofrontal duct would of course be directly continuous with the infundibulum ethmoidale in the adult. We can not say, however, that in such a condition, the sinus frontalis develops from the infundibulum ethmoidale. From adult relations it would appear as if the latter interpretation were correct; embryology, however, shows the error of this contention. If in the specimen shown in ﬁg. 41 the frontal sinus formation should take place from the cell of the second frontal furrow, the nasofrontal duct would be continued down to the infundibulum ethmoidale at an angle, but not be directly continuous with it. In the specimen shown in ﬁg. 43 (from a child aged 14 months) we ﬁnd the whole frontal recess extending and developing into the frontal sinus. In the latter case the adult sinus would in all probability have no true nasofrontal duct, but the sinus would open directly into the ventral and superior portion of the meatus nasi medius.
Note the possibilities of adult relations in the fetal specimens shown in ﬁgs. 39 and 40. In the specimen shown in ﬁg. 41 the infundibulum ethmoidale might continue its development or pouching lateral to the frontal recess and frontal furrows and thus form the frontal sinus. The aforementioned conditions are met with in the adult nose, and all may be accounted for by studying the varying fetal conditions. In a general way we may say, that when the frontal sinus develops from an anterior ethmoid cell, the adult sinus will have a nasofrontal duct—the tortuosity of the duct depending upon the cell from which the sinus developed and upon the degree of development and the disposition of the other anterior ethmoid cells. On the other hand, when the frontal sinus develops by a direct extension of the frontal recess there will in all likelihood be no true nasofrontal duct. Occasionally the adult frontal sinus has two nasofrontal ducts. This is explained by the fact that the sinus at times develops from two anterior ethmoid cells. In many instances the frontal sinus is in reality nothing other than an extensively developed anterior ethmoid cell.
The cellulae ethmoidales
The ethmoidal cells all develop from preformed furrows or recesses. They are nothing but extensions from some of the meatus nasi directly, or from the accessory recesses and furrows of the meatus nasi medius and superior. From the frontal furrows of the recessus frontalis, and from the furrows of the descending ramus of the meatus medius, the anterior group of ethmoid cells develop. From the ventral and superior extremity, and the superior and inferior recesses of the meatus superior; and the meatus suprerna I, the posterior group of ethmoid cells develop. The anterior group have, therefore, their ostia opening inferior to the attached border of the concha nasalis media, and the posterior group have their ostia opening superior to it. The so—called middle group of ethmoidal cells are thus classed with the anterior group, and the term ‘middle ethmoidal cells’ is dropped. This I think is a better classiﬁcation because the cells of the bulla are closely associated with the cells of the frontal recess.
The lateral masses of the ethmoid bone and its appendages, such as major and accessory conchae, are primitively solid structures. Later, however, the lateral masses become more or less honey-combed or labyrinth—like by the developing ethmoidal cells. The ethmoid cells, while primarily conﬁned to the lateral ethmoidal masses, frequently extend beyond these limits into the concha media, the processus uncinatus, and the agger nasi. The bulla ethmoidalis is practically always shell-like due to a cell or cells. Anterior ethmoid cells may develop far into the frontal region, and in many cases might be classed as frontal sinuses. In some adult specimens in which two large sinuses are present on the same side of the frontal region, it is diﬂicult to say whether they are both frontal sinuses or extensively developed anterior ethmoidal cells. Developmentally, in many cases, they are eth~ moid cells, and topographically they should be classed as frontal sinuses. Occasionally the posterior ethmoid cell which develops from the meatus nasi suprema I extends into the sphenoidal sinus. The superior and the supreme conchae usually become more or less shell—like in the adult due to the developing posterior ethmoid cells.
In the formation of the ethmoid labyrinth there is no unifor1n— ity. In a general way the anterior group of ethmoidal cells is ventral to the posterior group. There is, however, at times, considerable overlapping of the two groups. Each cell as it grows from a preformed furrow or recess tends more or less towards the cribriform plate of the ethmoid bone. Even though a certain cell has its anlage—point farther inferior than another cell, it may outgrow its neighbor and force the latter to progress in a direction other than to which it was primarily directed. Later the cells in the homeycombing of the lateral ethmoidal masses grow in almost any direction. Sometimes the intervening walls break down and larger single cavities are thus formed. Seydel very aptly says: “ . . . . die Zellen der verschiedenen Reihen stehen gewissermassen im Wettkampf mit einander, bald iiberwiegen die der einen, bald die der anderen Reihe. Daher verlaufen die Trennungslinien zwischen den Reihen keineswegs immer genau wie die Muschelurspri'1nge.” '
The sinus sphenoidalis
Of the sinus sphenoidalis little need be said in this paper. It is primitively nothing but a constriction from the dorsal and superior portion of the nasal fossa, a fact already pointed out by Dursy. This constriction of the nasal fossa in the formation of the anlage of the sphenoidal sinus is evident fairly early, and at birth the sinus is comparatively well advanced in most instances. Its further development depends of course, just as in the other sinuses, upon the simultaneous growth of the sac and the resorption of bone. In this manner the sphenoidal cavity becomes well established in the body of the sphenoid bone.
In the frontal section shown in ﬁg. 20 we have represented the manner of constriction of the superior and dorsal portions of the nasal fossae in the formation of sphenoidal-sinus anlages.
Later the sinuses are represented by very shallow pits and by
the 5th month of extrauterine life the sinuses are well established (ﬁg. 42).
5. Some Later Developmental Changes on the Lateral Wall as Presented in the Adult Nose
It is not necessary to consider the adult lateral nasal wall in detail since the general anatomy is so well known, and besides the descriptions of the late fetal conditions as given, would in a measure be duplicated in a detailed description of the adult lateral wall. There are, however, certain conditions and relations of great importance which develop much later, and varying opinions are entertained on some of these points. We will, therefore, in subsequent paragraphs consider the later developmental changes with especial reference to: (1) the number of ethmoidal conchae in the adult; (2) the ethmoid cells with especial reference to their ostia; (3) the ostia maxillaria; (4) the relations of the nasofrontal duct with especial reference to the manner of communication of the frontal sinus with the meatus nasi medius.
The number of ethmoidal conchae in the adult
In previous paragraphs we dwelt at some length on the number of ethmoidal conchae that are differentiated before birth. We found that the number varied from three to ﬁve; with four major conchal folds in the ethmoidal region rather common, and ﬁve not at all unusual. The concha suprema III early loses its identity in the vast majority of cases. This is also true of the concha suprema II; however it is as a rule somewhat farther delayed. The question naturally arises: How far does the reduction in ethmoidal conchae progress? and what is the average number of conchae in the adult in a large series of specimens?
Naturally in the cases where the meatus suprema I is very shallow and short, it becomes a personal equation as to whether the shallow furrow should be considered as a meatus or merely as a groove on the medial surface of the concha superior. In one case it means an extra concha; in the other the whole ethmoidal mass, superior to the concha media is considered as the concha superior. This is doubtless the reason why Writers differ so widely in their results. Again, the accessory concha in the meatus superior, when Well developed, is at times erroneously considered as the concha superior. This, of course, leads to divergent results as to the number of ethmoidal conchae that are present in the adult nose.
Zuckerkandl in “120 Kopfhalften” of adults found two ethmoidal conchae in 24 of them, and three ethmoidal conchae in 96 of them. In this number he found his “mittlere Siebbeinmuschel operkulisiert” in 11 instances. According to some of his ﬁgures he has at times considered my accessory concha of the meatus superior as his ‘mittlere Siebbeinmuschel.’ If we subtract 11 cases from the 96 and add them to the 24, we would presumably have a better ratio for comparison with other results. The accessory concha of the meatus superior is very prominent in some adult noses, and a large number of specimens show at least a rudimentary accessory concha.
The fourth annual report of the committee of collective investigation of the Anatomical Society of Great Britain and Ireland, gives the following results: Out of 152 observations, 3 cases are reported with but one ethmoidal concha; 85 cases with two ethmoidal conchae; 62 cases with three ethmoidal conchae; and 2 cases with four ethmoidal conchae. This report is the result of ﬁfteen subreports from as many different schools, with presumably a larger number of observers. It is, therefore, difficult in such a report to have uniformity in observation because, as stated before, the personal equation as to what should be considered a concha in the cases where the differentiation is slight, is obviously great. The report shows that in a few instances the reduction in ethmoidal conchae has progressed but little. The number of times that three ethmoidal conchae are present in the adult nose is rather low in the above report, as compared with the statements of other observers. Unless one continually remember the late fetal conditions, he is apt, in many cases, not to recognize the concha suprema I in the adult nose, 75.3., when the concha is very rudimentary.
FIG. 45 (X 10) Drawing of a frontal section through the lateral wall of the nasal cavity of a 7-months fetus (eries C, slide 8). The section is in the region of the accessory concha of the superior meatus. It shows the well developed ‘crista suprema’ of the concha media, also the marked curling of the latter concha.
I recently examined 120 adult lateral nasal walls, with especial reference to the number of major ethmoidal conchae. I found that 75 specimens presented three ethmoidal conchae, and the remaining 45 specimens but two ethmoidal conchae. A few of the specimens were suggestive of having four ethmoidal conchae. I ﬁnd that the ostium of the ethmoidal cell which develops from the meatus suprema I is very often a good point for orientation in determining the presence of a concha suprema I (adult).
According to Zuckerkandl’s series and the series I examined, we should consider the adult ethmoidal region as usually presenting three ethmoidal conchae rather than two.
The ethmoid cells and their ostia
In a previous paragraph on the anlages of the ethmoidal cells we divided them into two groups—anterior and posterior. All those cells that have their ostia opening inferior to the attached border of the concha nasalis media may be designated as anterior ethmoidal cells; and those that have their ostia opening superior to the attached border of the concha nasalis media may be designated as posterior ethmoidal cells. The anterior group are in a general way ventral to the posterior group; however there is at times considerable overlapping of the two groups.
The posterior group of cells.
The posterior group of cells communicate with the meatus nasi superior and suprema I. The latter meatus is present, according to my specimens, in 62.5 per cent of cases; and 75 per cent of the positive specimens have aposterior ethmoid cell opening into this meatus. In some instances the cell which opens into the meatus suprema I is very large and it may encroach upon the lumen of the sphenoidal sinus. Rarely two posterior ethmoidal cells communicate with the meatus suprema I.
It is a constant condition to have posterior cells opening into the superior meatus. According to my specimens we invariably have a posterior ethmoid cell opening at the superior and ventral extremity of the superior meatus. The latter cell very frequently extends into the body of the concha media, and at times is excessively large. In previous paragraphs we spoke of an accessory concha of the superior meatus. We will recall the presence of recesses, inferior and superior to the latter concha——these recesses early giving evidence of cell-anlages. If we carefully look over a series of adult specimens we will in many cases see evidences of this accessory concha, which at times is Well formed. Since the fetus gave evidence of developing cells from the two recesses mentioned We would in the adult expect to ﬁnd ostia of posterior ethmoidal cells in these positions. TWenty—six per cent of my specimens showed a posterior cell opening in the position of the superior recess, and in 50 per cent of cases a posterior cell opened in the position of the inferior recess.
To recapitulate: The posterior ethmoidal cells open into the meatus nasi superior and suprema I. The latter meatusis present in 62.5 per cent of adult cases, and in 75 per cent of instances this meatus has a posterior ethmoidal cell communicating with it. The superior meatus has in 100 per cent of cases a cell communicating with it at its ventral and superior termination. The superior meatus has also in 26 per cent of instances a cell opening into the superior recess, and in 50 per cent of cases a cell opening into the inferior recess.
These adult conditions justify our conclusions with reference to cell-anlages in the fetus and young child.
The anterior group of cells.
It will be recalled that we referred to anlages of anterior ethmoidal cells in both the ascending and descending rami of the meatus nasi medius, 73.6., in the regions of the bullar furrows and the frontal recess. If now we examine a series of adult specimens we will notice in the positions of the former cell—anlages that we now have ostia of cells. My series of specimens indicate that in 100 per cent of cases anterior ethmoid cells have their ostia in the position of the suprabullar recess or furrow. The cells that open in this position vary in number from one to three. They are directed variously behind the bulla ethmoidalis, thus causing the latter structure to be hollowed out and shell-like and at times excessively large. Some of the cells with their ostia in the position of the suprabullar recess may also be directed towards the cribriform plate or towards the frontal sinus. I ﬁnd in 13 per cent of instances that there is an ostium on the medial surface of the bulla ethmoidalis, or in the position of the original bullar furrow (ﬁg. 31). In 11 per cent of cases an ostium is found in the position of the infrabullar furrow. The cells that communicate with the middle meatus in the location of the latter two places are usually very small.
The anterior ethmoidal cells that develop in the region of the ascending limb of the middle meatus, 12.6., in the region of the frontal recess, are very variable in size and position. The number of adult cells depends largely upon the degree of differentiation of frontal furrows in the fetus. Some of the cells in this position open directly into the middle meatus, others into the superior and ventral extremity of the infundibulum ethmoidale. Some also open into the suprabullar recess. Some of these anterior ethmoidal cells may extend towards the frontal sinus so that it is difficult to say whether the cavity is that of a frontal sinus or that of an anterior ethmoidal cell. The ventral and superior end of the infundibulum ethmoidale also frequently expands into an anterior ethmoidal cell, which at times is large.
The conchal cells
As was stated in a previous paragraph there is no uniformity in the development and arrangement of the cells of the ethmoid labyrinth. It will be recalled that the cells develop from preformed furrows, and that the former gradually extend into the lateral masses of the ethmoid bone. In this manner the lateral ethmoidal masses which were primitively solid structures become more or less labyrinth-like as age advances. The individual cells are usually separated by thin osseous plates, or as in some adult cases, merely by mucous membrane—the bony partition having been resorbed. Again the intervening walls may be entirely gone and one or the other group of cells may be replaced by a large cavity. Many of the ethmoid cells are completed by the articulation of the ethmoid with neighboring bones.
These cells in many cases are not conﬁned to the limits of the lateral ethmoidal masses. They hollow out the superior and supreme ethmoidal conchae so that in the adult these conchae are merely thin she1l—1ike medial boundaries of posterior ethmoidal cells. The cells also at times extend into the sphenoidal sinuses, and also encroach upon the lumina of the frontal sinuses. Should the intervening walls break down we would have established a communication between either of the sinuses and certain of the ethmoidal cells. Ethmoid cells very frequently extend into the ventral extremity of the concha. media, into the ventral extremity of the processus uncinatus, and into the agger nasi. The bulla ethmoidalis is almost invariably shell—like because of air cells. At times the concha nasalis media contains multiple air cells or it may contain a Very large single cell which causes the concha to look bleb-like. It is very common for the posterior ethmoid cell which develops from the ventral and superior extremity of the meatus nasi superior to extend beyond the limits of the lateral ethmoidal mass into the concha media. Sometimes a cell develops from the so-called sinus of the concha media, which more or less hollows out the ventral extremity of the concha. Anterior ethmoidal cells may also extend into the concha media. The cells that extend into the agger nasi and processus uncinatus may communicate either with the meatus medius directly or with the superior and ventral extremity of the infundibulum ethmoidale. The concha nasalis media at times curls laterally and superiorly and thus forms the so—called sinus of the middle concha. This curling is, however, not extensive as a rule and the area included by it always opens freely into the middle meatus. It is usually unimportant.
These conchal cells have led to conﬂicting and some erroneous theories as to their genesis. Theysurely are nothing other than ethmoidal cells which have developed beyond the limits of the lateral ethmoidal masses into the appendages of these masses, z'.e.,into the conchae. Occasionally a cell develops into the concha media which has its anlage-point on the lateral surface of this concha (ﬁgs. 34 and 3.5).
These conchal cells may become the seat of pathological conditions, just as do the other paranasal chambers, but the cells do not in any manner owe their origin to such conditions. For a further consideration on conchal cells the reader is referred to a previous paper bearing directly on these cells.
The ostia maxillaria
In this connection little need be said about the ostium maxillare. In the adult it of course is in the position of the primitive sinus maxillaris, i.e., the adult ostium corresponds in position to the evagination of the mucous membrane in the infundibulum ethmoidale for the formation of the anlage of the sinus maxillaris. The formation of the ostium maxillare was, therefore, considered in previous paragraphs and nothing further need be added here. While the ostium maxillare may be primitively double, i.e., the anlage of the sinus maxillaris may be represented by a double pouching, it (the ostium) at times becomes duplicated later in life. This latter duplication of the ostium needs to be considered since certain later developmental processes are involved. Very frequently there is also an ostium present in the adult nose which communicates directly between the sinus maxillaris and the meatus nasi medius. This ostium is not present in the fetus and young child, hence a later developmental process is here involved. In order to complete the consideration of the various developmental stages of the lateral nasal wall it will be necessary brieﬂy to consider the duplication of the ostium maxillare and the ostium maxillare accessorium.
The ostium maacillare accessorium. In a previous paper I referred to the frequent occurrence of an accessory aperture of the sinus maxillaris. In the same article I dwelt brieﬂy on the theories held by several writers as to the genesis of this opening, and stated that I hoped to study the accessory aperture more extensively in the fetus and child, to see whether the opening, after all, at times, did not have an embryological signiﬁcance. Since then I have had the opportunity of examining a larger number of specimens of the lateral nasal wall of the adult, child, and fetus.
This accessory ostium is, as arule, situated in the membranous portion of the lateral wall of the middle meatus, a short distance above the cephalic and attached border of the inferior nasal concha, at about the junction of its middle and posterior thirds. In some instances the accessory ostium is found immediately dorsal to the infundibulum ethmoidale— occasionally actually extending into the latter. This accessory ostium is usually single but occasionally it is duplicated, and rarely three accessory apertures are present in this portion of the middle meatus. The aperture must not be confused with the duplication of the ostium maxillare which is located in the depth of the infundibulum ethmoidale; however at times very near its dorsal extremity.
Nathaniel Highrnore, who apparently was the ﬁrst anatomist to describe the maxillary sinus, does not mention anything about this accessory ostium. J. Cruveilhier refers to an oriﬁce in the middle meatus, apparently the accessory ostium of the sinus maxillaris, which he considers the “plus ordinairement l’oriﬁce du sinus mascillaire.” Further he says that “Cet oriﬁce semble manquer quelquefois; on le trouve alors au niveau de la partie moyenne de l’infundibulum; on dirait, dans ce cas, que le sinus maxillaire communique directement avec les sinus frontaux et non avec les fosses nasales.” He also calls attention to the fact that the maxillary sinus may possess two apertures: “Il n’est pas rare de Voir le sinus maxillaire communiquer a la fois et dans le méat moyen et dans Pinfundibulum.”
From the above we must conclude that Cruveilhier considered the accessory aperture as the more regular ostium of the sinus maxillaris, but recognized that it is inconstan-t. He erroneously thought that the ostium maxillare, which is constant and communicates with the infundibulum ethmoidale, was not always present, and when it was present, that the maxillary sinus communicated with the frontal sinus and not with the middlemeatus. We only rarely have direct communication between the frontal and maxillary sinuses (Cryer, Brophy, and Schaeffer have reported such cases). While from a practical point of view the frontal sinus communicates with the maxillary sinus in many cases, due to the infundibulum ethmoidale acting as a gutter between the frontal region and the ostium maxillare, We have no right to say that the two sinuses are in communication with each other directly. In all cases the sinus maxillaris communicates indirectly with the meatus medius by way of the the hiatus semilunaris. Gosselin, however, recognized that the sinus maxillaris constantly communicated with the ‘Trichter’ (infundibulum ethmoidale). Henle ﬁgures an accessory opening of the sinus maxillaris under the name ‘unbestandige Communicationsoffnung.’
Giraldes in 100 cadavers found this accessory ostium “acht bis zehn Mal.” Zuckerkandl reports it present “in jedem neunten bis zehnten Falle.” Chiari and Hajek found an accessory ostium in every ﬁfth case. Turner found it four times in nine dissections. In a former paper I reported an accessory maxillary ostium present thirty ﬁve times out of 80 specimens examined, or a percentage of 43.75. Three of the specimens presented two accessory ostia, or a percentage of 3.75.
Since the publication of the aforementioned paper my attention was directed to a report (Fourth annual report of the committee of collective investigation of the Anatomical Society of Great Britain and Ireland) which was inadvertently overlooked before. This report covers the examination of 152 specimens. In this number of specimens it was found that 53 percent of maxillary sinuses possessed but one aperture (presumably the ostium maxillare); 44.1 per cent, two apertures (presumably the regular ostium, and either the duplication of the latter or the ostium accessorium); and 2.9 per cent, three apertures (presumably two accessory ostia besides the regular aperture). The sinus maxillaris communicated with the infundibulum ethmoidale by two apertures (a duplication of the regular ostium) in 17.6 per cent of cases. In this report no mention is made as to what is considered a duplication of the normal aperture. In some cases an accessory ostium is placed immediately dorsal to the infundibulum ethmoidale, in fact is very often continuous with the infundibulum. I imagine that some of the latter cases are included among the 17.6 per cent of specimens. Unless the opening were Wholly included within the dorsal end of the infundibulum I considered the aperture as an accessory ostium, communicating directly between the sinus maxillaris and the meatus nasi medius, and not as a duplication of the ostium maxillare proper. With this fact kept in mind the above report agrees closely with the ﬁgures hi my former paper and also with the results obtained in the following series.
I recently examined 125 adult specimens (including those of my former series) of the lateral nasal wall and found that 53 of them had accessory ostia communicating directly between the maxillary sinus and the middle meatus——a percentage of 42.4. Three of the specimens presented two such openings—a percentage of 2.4.
J. A. Giraldes was apparently the first to consider this opening from a developmental point of view. He came to the conclusion “dass in allen Fallen, W0 diese abnorme Oeffnung besteht, sie immer das Product eines pathologischen Vorganges und durch eine wirkliche Perforation zu Stande gekommen ist.” He however, considered this aperture much less common than it is, thinking it present in only 8 or 10 per cent of instances. Giraldés bases his pathological theory on the fact that he had the privilege of following the “Entwicklungsphasen Von der Verdﬁnnung der Schleimhaut des Ganges bis zur volstandingen_Durchbohrung.” Zuckerkandl corroborates the thinning of the mucous membrane, but does not hold to the pathological theory. The latter author has seen some cases where an accessory aperture was caused by the gradual wearing of a “zugespitzer Hakenfortsatz der N asenscheidewand,” which ﬁnally resulted in an opening on the lateral wall of the middle meatus.
While some accessory apertures are obviously due to a pathological process as suggested by Giraldés, and others are caused in a mechanical manner by spurs on the nasal septum, as suggested by Zuckerkandl, we certainly must look elsewhere in the vast majority of cases to ﬁnd the genesis of this very common aperture.
I agree that there is a thinning of the mucous membrane in the position of the accessory ostium, but believe that the explanation for this is found in the development of the sinus maxillaris. In infancy the walls of the sinus maxillaris are comparatively very thick. We know that the sinus cavity increases by the simultaneous growth of the sac and the resorption of surrounding tissue, these processes taking place pari passu with the growth of the face. In this manner the sinus walls become thinner, up to a limit, as age advances. The thinning out apparently progresses unevenly, as evidenced by the Very uneven walls of many adult cavities. On the base or medial wall of the cavity we have an area that is in time composed of merely two layers of abutting mucous membrane, one the mucous membrane of the middle meatus, and the other the mucous membrane of the maxillary sinus. These two layers of mucous membrane with no intervening bone oﬁers very little resistance to the growing maxillary cavity. In time they become so thinned out and attenuated in many instances that ultimately an opening is formed, thus establishing the ostium maxillare accessorium. This reminds one of the early thinning and attenuation and ultimate rupture of the two layers of abutting epithelium—the bucconasal membranes—-in the establishment of the primitive choanae.
If we accept this view, and to me it seems plausible, as to the genesis of the ostium maxillare accessorium, we would not expect to ﬁnd the ostium in fetuses nor in young children. We would neither expect to ﬁnd this accessory aperture often in the young adult, 1I.e., before the twentieth year of age. We would, however, especially look for it in the more advanced adult, after the walls of the sinus maxillaris have been thinned out by the large adult cavity. This is in accord with my results. I have never been able to ﬁnd the ostium maxillare accessorium in the fetus nor in the child. It occurs, as far as my observations would indicate, only in the adult. I have found it in adults between the ages of twenty and ninety years. It is avery frequent aperture from thirty-ﬁve years on. Symington likewise never found the accessory ostium in children. He says: “In children I have never found more than one aperture, viz., that into the infundibulum.”
I have, therefore, come to the conclusion that the ostium maxilare accessorium is in most instances established by the developing sinus maxillaris. The growth of the sinus causes the two layers of abutting mucous membrane to become thinned out and attenuated, ultimately resulting in an opening in very many adult noses. Some are doubtless due to a pathological process, and others produced in a mechanical manner by septa] spurs. Enlarged middle conchae may also wear holes into the maxillary sinus in this position; this is, however, rare.
The duplication of the ostium maxillare. In a previous paragraph I spoke of the double pouching of the primitive maxillary sinus. By the distal fusion of the two pouches the points of evagination would remain as the adult ostia maxillaria, yet the adult cavity would be single. Other duplications of the regular maxillary ostium are doubtless caused in amanner similar to the establishment of the ostium accessorium, z'.e., by the attenuation and ultimate rupture of the mucous membrane in this position. The same conditions prevail here as in the position of the ostium accessorium, since it is in the immediate neighborhood.
F: G. 46 A semidiagrammatic drawing of an adult lateral nasal wall. The concha nasalis media is represented as partly cut away so as to expose the underlying structures. Note the nasofrontal relations, and that there is no true nasofrontal duct. The frontal sinus presumably developed by an extension of the frontal recess directly. Compare this with the conditions represented in ﬁgs. 47, 48, and 49.
The communication of the frontal sinus with the middle meatus
We previously considered the early conditions of the frontal recess with especial reference to the frontal furrows found on its lateral Wall. Reference Was made to the possible points of origin of the sinus frontalis. It now remains brieﬂy to consider the ventral and superior portion of the meatus medius with especial reference
FIG. 47 A semidiagrammatic drawing of an adult lateral nasal Wall. The concha nasalis media is represented as partly cut away. Compare the nasofrontal relations with those found in ﬁg. 46. In this case there is a nasofrontal duct which meets the infundibulum ethmoidale at an angle. Some of the secretion from the frontal sinus would ﬁnd its way directly into the meatus medius, and the remainder would pass into the superior and ventral portion of the infundibulum ethmoidale.
The frontal sinus in this case presumably developed from an anterior ethmoid cell.
to the manner of communication of the frontal sinus with the middle meatus in the adult, to see whether our earlier conclusions on this portion of the lateral nasal wall were justifiable. We previously concluded that the frontal sinus might develop from the frontal recess directly; from one or more anterior ethmoid cells which developed from the frontal furrows; from the recess and a cell ; or rarely by direct extension of the superior and ventral extremity of the infundibulum ethmoidale. In ﬁgs. 46 to 49 We have semidiagrammatic representations of prevailing adult types of nasofrontal relations.
In ﬁg. 46 the frontal sinus is continued down to the frontal recess, that is, to the ventral and superior portion of the meatus medius. In such a case there is no true nasofrontal duct and presumably the frontal sinus developed by a direct extension of the frontal recess. Note that the infundibulum ethmoidale ends in an air cell and that it is not continuous with the frontal sinus. Occasionally in these instances the infundibulum ethmoidale is carried much nearer to the frontal sinus, and secretion from the latter may drain almost directly into the ventral and superior portion of the infundibulum.
In ﬁg. 47 there is a nasofrontal duct. This represents a very common condition. Note that while the infundibulum ethmoidale is not continuous with the nasofrontal duct it nevertheless meets the latter duct at an angle. Secretions from the frontal sinus would drain partly into the infundibulum ethmoidale and partly into the middle meatus directly. Doubtless the frontal sinus in such instances developed by the extension of an anterior ethmoidal cell that had its origin in one of the frontal furrows.
In ﬁg. 48 we again have the representation of a prevailing condition or type. There is again a nasofrontal duct, but it is not in line with the infundibulum ethmoidale. Practically all secretion from the frontal sinus would drain into the meatus nasi medius. We must here conclude that the frontal sinus developed by an extension of an anterior ethmoidal cell, presumably the cell from the ﬁrst frontal furrow.
In ﬁg. 49 the infundibulum ethmoidale is continuous with the nasofrontal duct. There are two possibilities of development for the frontal sinus in these cases. In the ﬁrst place the infundibulum ethmoidale may have continued its development superiorly and ventrally, lateral to the frontal furrows, a.nd then enlarged into the frontal sinus. Another explanation may be found in the fact that the infundibulum ethmoidale may have been continuous with a frontal furrow; if not continuous, the intervening lamella of tissue may have been resorbed and the two channels thus made continuous. It is not common for the tnfundibulum ethmoidale to be DIRECTLY continuous with the nasofrontal duct. At ﬁrst sight it may appear so, but careful dissection will show that, in the majority of cases where intimate relations exist between the in fundibulum ethmoidale and the nasofrontal duct, the two channels meet each other at varying angles. At times there is actually a slight groove connecting the two channels. We have, however, no right to say that in such cases, the nasofrontal duct is directly continuous with the ventral and superior end of the infundibulum ethmoidale.
FIG. 48 A sernidiagrammatic drawing of an adult lateral nasal wall. The colicha media is again represented as partly cut away so as to expose the operculated structures. Compare the nasofrontal relations with those represented in ﬁgs. 46 and 47. Practically all of the secretion from the frontal sinus would drain directly into the meatus nasi medius. The frontal sinus is doubtless an extension of an anterior ethmoidal cell. '
In ﬁg. 50 anterior ethmoidal cells from two frontal furrows are developed sufficiently to be called frontal sinuses. Both communiCate with the frontal recess or the Ventral and superior portion of the meatus medius. In such instances the intervening wall may break down and an adult frontal sinus with two nasofrontal ducts will be present. Occasionally we find a frontal sinus with two ducts leading from it, and the above explanation for such a condition seems plausible.
FIG. 49 A semidiagrammatic drawing of an adult lateral nasal wall. The conchu. nasalis media is partly cut away. The infundibulum ethmoidale is directly continuous with the nasofrontal duct——a condition not common.
If we take all the cases that fall under the types as represented by ﬁgs. 47 and 49, they will include about 56 per cent of my specimens, type, ﬁg. 47, being much the more common of the two. In a previous paper these two types were included among the specimens as representing positive fronto-maxillary relations. The specimens falling under the type as represented by ﬁg. 46 will also frequently fall under the above classiﬁcation. The specimens falling under the t-ype as is represented by ﬁg. 48 will include approximately 40 per cent of my adult specimens. The latter were in a previous paper included among the specimens as representing negative fronto-maxillary relations. Specimens will, of course, now and then differ somewhat from these types, but they will all in a general way fall under one or the other group.
FIG. 50 A semidiagrammatic drawing of an adult lateral nasal wall. The concha. media is partly cut away so as to expose for study the underlying parts. It gives evidence of three primitive frontal furrows, viz., two frontal sinuses which doubtless developed from anterior ethmoid cells, and a third cell which extends towards the agger nasi. The region of the frontal recess is well shown in the drawing.
In this manner we can account for two frontal sinuses on one side. We can also account for the so-called absence of a frontal sinus. Should‘ the frontal recess or an anterior ethmoidal cell of a frontal furrow, stop short of the vertical portion of the frontal bone we would of course have a diminutive frontal sinus-—in fact no frontal sinus as far as position is concerned. We must, however, remember that the first evidences of the frontal sinus Lateral Wall of the Cavum Nasi in Man. 699
must not be sought in the vertical portion of the frontal bone but in the superior and ventral portion of the meatus medius, 13.6., in the frontal recess. The developing frontal sinus may not progress farther than the horizontal portion of the frontal bone. The different views held on the presence and absence of the frontal sinus is doubtless due to differences of opinion as to what should be called a frontal sinus, and how far the development must progress towards the frontal region before the cell has reached the dignity of a frontal sinus.
1. The nasal anlage establishes itself about the third week of embryonal life as localized thickenings of the ectoderm, located on both sides of the outer surface of the wall of the fore-brain, immediately superior to the primitive oral fossa.
2. During the fourth week the nasal areas become passively depressed, due to an increase in the thickness of the surrounding mesenchyme. In this manner the nasal pits become formed.
3. For some time the nasal pits communicate freely with the primitive oral fossa. The maxillary and the lateral nasal processes abut and fuse with the medial nasal processes, thus separating the nasal pits from the oral fossa. ‘
4. For some time the lines of fusion of the maxillary and the lateral nasal processes with the medial nasal processes are represented by strands of ectodermal tissue. These ectodermal fusionlines soon disappear ventrally and are replaced by mesenchyme; z'.e., the mesenchymal tissue of the maxillary and lateral nasal processes becomes continuous with that of the medial nasal processes.
5. Farther dorsally the ectodermal tissue between the fused maxillary and medial nasal processes does not wholly disappear, but strands of ectodermal tissue remain at the points of fusion. This ectodermal tissue thins out and ultimately‘ ruptures, thus establishing the primitive choanae.
6. The nasal pits deepen dorsally and superiorly, and in a 35-day embryo the olfactory organ is represented by two blindly ending pouches lying in the mesenchymal tissue above the oral cavity. These blind pouches may be termed the primitive nasal fossae.
7. The dorsal extension of the blind primitive nasal fossae continues until the ectoderm of the nasal fossae meets the ectoderm of the oral cavity. We have now in these positions merely thin membranes composed of two layers of abutting epithelium~ nasal and oral~separating the dorsal portions of the primitive nasal fossae from the oral cavity.
8. These membranes~the membranae bucconasales——become attenuated and thinned out, ultimately resulting in rupture. In this manner the primitive choanae are established, and again a communication between the nasal fossae and the oral cavity. The primitive choanae are established approximately from the 35th to the 38th day of embryonal life.
9. When ﬁrst formed the nares communicate freely with the exterior, but shortly afterwards, in many cases, they become plugged by an overgrowth of epithelium. This plugging may be complete or more or less fenestrated in character.
10. With the formation of the primitive choanae we have also established the primitive palate, z'.e., the portion of the roof of the primitive oral cavity extending from the primitive choanae to the nares.
11. The palatal processes; by fusing along their opposed edges in the median plane; establish the deﬁnitive palate. In the formation of the deﬁnitive palate the nasal fossae appropriate a considerable portion of the primitive oral cavity.
12. The nasal cavity which is early divided anteriorly by the medial nasal processes, becomes divided into fossae farther dorsally by the growth and fusion of the nasal septum with the mid-palate line. This division of the nasal cavity into fossae takes place from before backwards.
13. Coincidently with the formation of the deﬁnitive palate the primitive choanae elongate and ultimately come to occupy the position of, and thus become, the permanent choanae.
14. The lateral nasal wall is at ﬁrst extremely simple, and it presents no evidence of its later complexity. Lateral Wall of the Cavum Nasi in Man. 701
15. The ﬁrst change on the lateral nasal wall from amorc or less even surface is the production of very shallow grooves. The latter appearing inferior and superior to the position of the primitive concha nasalis inferior (maxillary fold). These shallow grooves at once throw into slight relief the greater portion of the lateral nasal wall~the anlage of the concha nasalis inferior.
16. Shortly after the ﬁrst a second fold appears, outlining the anlage of the ethmoidal conchae.
17. From three to ﬁve ethmoidal conchae become differentiated before birth.
18. The ethmoidal conchae in a general way present ascending and descending crura. The ascending crura are, however, in many cases not well differentiated. At times the ascending crura are represented by a general ascending-crural mass, but individual ascending crura are not outlined.
19. The ethmoidal meatuses, including the meatus nasi medius, also in a general way present ascending and descending rami. The descending rami are, however, by far the most marked. In fact many ethmoidal meatuses have no ascending rami. The ascending ramus of the meatus medius is the best outlined. Occasionally the meatus superior possesses a well marked ascending ramus.
20. The integrity of the ethmoidal conchae and meatuses depends upon the descending limbs rather than upon the ascending limbs.
21. The ascending and the descending rami of the meatus medius present accessory conchae and furrows which are comparable to structures found in other mammals.
22. The descending ramus of the meatus superior also presents an accessory concha on its lateral wall. It is at times well marked, and again it may be very rudimentary or be entirely wanting.
23. In the region of the knees or bends of the ethmoidal conchae we frequently ﬁnd lobules, and on these lobules secondary nodules are occasionally seen.
24. The descending ramus of the concha nasalis media very frequently presents furrows on its medial surface. One of these furrows at times more or less divides the concha into superior and inferior portions.
25. The sinus paranasales all develop from preformed furrows or pits, with the single exception of the sinus sphenoidalis which is primitively nothing but a constriction from the dorsal and superior portion of the nasal fossa.
26. The sinus maxillaris develops by an evagination from the infundibulum ethmoidale. The primitive sinus may be duplicated, in that the pouching is occasionally double. The primitive pouching is at times extensive, including a goodly portion of the infundibulum ethmoidale. These facts doubtless account for the very large ostium maxillare of some adults and the duplication of the ostium maxillare in some cases.
27. The sinus frontalis may develop either from the frontal recess or from an anterior ethmoidal cell. It may also have a double origin, 13.9., from two anterior ethmoidal cells, or from an ethmoidal cell and the frontal recess. Rarely it develops by a direct extension of the infundibulum ethmoidale.
28. The anterior group of ethmoidal cells develop from the frontal furrows of the ascending ramus of the middle meatus, and from the furrows found on the lateral wall of the descending ramus of the middle meatus. The infundibulum ethmoidale at its superior and ventral termination very frequently dilates into an anterior ethmoidal cell.
29. The posterior group of ethmoidal cells develop from the superior and ventral end of the superior meatus, from the superior and inferior recesses of the superior meatus, and from the meatus suprema I. The latter meatus persists in about 62.5 per cent of cases.
30. We should consider the adult ethmoidal region as usually presenting three conchae rather than two.
31. In the adult the posterior ethmoidal cells open into the meatus nasi superior and suprema I. The latter meatus is present in 62.5 per cent of my adult specimens, and in 75 per cent of instances this meatus has a posterior ethmoidal cell communicating with it. The superior meatus has in 100 per cent of cases a posterior ethmoid cell communicating with it at its ventral and superior termination. The superior meatus has also in 26 per cent of instances a cell opening into the superior recess, and in 50 per cent of cases a cell opening into the inferior recess.
32. In the adult the anterior ethmoid cells open into the meatus medius. According to my series of specimens, in 100 per cent of instances anterior ethmoid cells have their ostia in the position of the suprabullar recess or furrow. The cells that open in this position vary in number from one to three, and are directed variously behind the bulla ethmoidalis. They may also be directed towards the cribriform plate or towards the frontal sinus. I ﬁnd that in 13 per cent of cases there is an ostium of an anterior ethmoid cell on the medial surface of the bulla ethmoidalis, or in the position of the original bullar furrow. In 11 per cent of instances an ostium of an anterior ethmoid cell is found in the position of the infrabullar furrow. The anterior ethmoid cells that develop from the frontal furrows vary in size, number, and position. These cells may open directly into the middle meatus or into the superior and ventral end of the infundibulum ethmoidale. Some of them also frequently open into the suprabullar recess.
33. Ethmoid cells frequently extend into the body of the concha nasalis media, the agger nasi, and the processus uncinatus. These cells also at times encroach upon the cavities of the frontal and sphenoidal sinuses. '
34. The ostium of the adult sinus. maxillaris is frequently duplicated. This may be due to a double pouching of the primitive sinus maxillaris, or it may be developed later in a manner similar to the formation of the ostium maxillare accessorium.
35. The sinus maxillaris has, according to my series of specimens, an accessory ostium communicating with the meatus medius directly in 42.4 per cent of cases. I believe that this accessory ostium is formed by the developing sinus maxillaris, i.e., the sinus maxillaris developing until the medial wall of the cavitybecomes thinned out and attenuated in the position of the accessory opening, until an ostium is formed. The accessory ostium is not present in the fetus nor in the young child.
36. In the adult the sinus frontalis may communicate with the meatus nasi medius in one of the following ways: (1) The nasofrontal duct or the sinus frontalis may open directly into the meatus medius; (2) The nasofrontal duct may be directly continuous with the infundibulum ethmoidale; (3) The nasofrontal duct may be continued down to the infundibulum ethmoidale and meet the latter structure at varying angles; (4) The sinus may have two nasofrontal ducts which in turn may have either of the above relations with the cavity of the nose; (5) Rarely the sinus frontalis communicates directly with the sinus maxillaris.
37. In some case the sinus frontalis has no true nasofrontal duct, but the sinus cavity itself extends well down into the superior and ventral portion of the meatus medius.
38. It is not common for the infundibulum ethmoidale to be directly continuous with the nasofrontal duct. As a rule the nascfrontal duct meets the infundibulum ethmoidale at varying angles. There is frequently a shallow groove connecting the two channels. However some specimens show that the infundibulum is directly continuous with the nasofrontal duct.
39. If we include the cases in which the infundibulum ethmoidale is directly continuous with the nasofrontal duct, and those in which the nasofrontal duct meets the superior and ventral end of the infundibulum ethmoidale at an angle, they will represent approximately 56 per cent of my specimens. The specimens in which the nasofrontal duct communicates directly with the meatus nasi medius will include approximately 46 per cent of my specimens. The cases in which no nasofrontal duct is present, and those in which two nasofrontal ducts present are distributed among the above specimens, since they can all be thus classiﬁed."
40. From a practical point of view the infundibulum ethmoidale acts as a gutter communicating between the frontal region and the maxillary sinus in 56 per cent of my cases.
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