Talk:Paper - Injection and reconstruction of the jugular lymph sac in the chick (1912)
Injection And Reconstruction Of The Jugular Lymph "Sac" In The Chick
Clark EL. Injection and reconstruction of the jugular lymph "sac" in the chick. (1912) Anat. Rec. 6: 263-.
Eleanor Linton Clark
From the Anatomical Laboratory of The Johns Hopkins University
It has recently been pointed out that the present difference of opinion in regard to the mode of development of the lymphatic system is due largely to the method employed in studying the subject. Those authors who have used exclusively the method of reconstruction from cross sections, have represented the earliest lymphatics as isolated channels and spaces. From this two theories have arisen:
1. The view tentatively advanced by F. T. Lewis that the development is by the addition of portions of blood capillaries which have been cut off from the general blood vascular system; and
2. The theory championed vigorously by Huntington, McClure and others, that the extension of lymphatics is by the transformation and addition of isolated spaces in the mesenchyme.
On the other hand, the theory of centrifugal growth has been brought forward by Ranvier, Sabin, MacCallum and Hoyer, who used the method of injection as Well as the study of cross sections, and by Clark who based his work on observations of living lymphatics. These authors picture the early lymphatics as continuous and state that their extension is accomplished by sprouting of the endothelium.
The limitation of the reconstruction method has been amply tested by Clark who made careful drawings of living lymphatics in the tadpole's tail and subsequently attempted to reconstruct these same vessels. Similar tests were made by Sabin on the embryo pig, to compare the method of reconstruction with that
262 ELEANOR LINTON CLARK
of injection. These studies made it clear that the lymphatics cannot be c.ompletely reconstructed, for vessels which in the living embryos and in injected specimens are seen to be continuous, appear in cross sections as isolated spaces. This accounts for the discrepancies in the chief views concerning the development of lymphatics.
The recent publication by A. M. Miller ^ in The American Journal of Anatomy has given me the opportunity to compare the value of the two methods in studying the development of the jugular lymph sac in the chick, since I have succeeded in making numerous injections of the same region and stages which Miller has reconstructed. These injections show that in chicks between five and one-half and seven days the developing lymph 'sac' which appears in Miller's reconstructions as a scattered group of isolated 'islands and channels,' is in reality a dense and continuous lymphatic plexus.
The accompanying drawing, fig. 2, was made from an injected specimen of the jugular lymphatic plexus in a chick of the same size and stage as fig. 1 (reprinted from fig. 3 in Miller's paper), judging by the measurement and by the appearance of the neighboring veins. A comparison of the two demonstrates again that much of the early lymphatic system cannot be seen in cross section and therefore cannot be reconstructed.
Students of chick embryology have always encountered difficulties in determining with accuracy the various stages, on account of the evident variations in the degree of development of two embryos of the same age or measurement. From Miller's descriptions it is not possible to determine the exact stages presented in his figures. Therefore in case my figure may not represent exactly the same stage as Miller's fig. 3, it may also be compared with his fig. 1, which shows a chick of the same age as my specimen, or with his fig. 4 which shows a reconstruction of an older embryo. In any case the contrast between the continuous plexus disclosed by injection and the isolated islands shown by reconstruction is most striking.
^A. M. Miller, "The Development of the Jugular Lj'mph Sac in Birds," American Journal of Anatomy, Vol. 12, No. 4, p. 473, Jan. 1912.
INJECTION AND RECONSTRUCTION
Fig. 2. Lateral view of jugular lymphatic plexus of the right side in a chick embryo incubated five days and twenty hours, measuring 14 mm., greatest length, after fixation. By means of a very fine glass canula (about 15 micra in diameter at the tip) dilute India ink was injected, under the binocular mircoscope, directly into one of the superficial lymphatics of the body wall, between the arm and leg. From here the ink filled the deep jugular lymph plexus and from it a few granules entered the vein through five connections (C). The drawing was made with the assistance of a camera lucida with a Zeiss binocular, oculars no. 4, objectives A3. Enlarged 50 diameters. A, vessel connecting the superficial lymphatics, into which the injections were made, with the jugular lymphatic plexus; A.C., anterior cardinal vein; P. C, posterior cardinal vein; D. C, duct of Cuvier; C, communications between jugular lymphatic plexus and vein; D., deep lymphatic, T. E. v., thoraco epigastric vein; C. L. D., cervical lymphatic duct.
Compare with Fig 1, which is a reprint of Miller's diagram drawn from a reconstruction of this region in a chick of approximately the same stage.
264 ELEANOR LINTON CLARK
I have also made injections in chicks of seven days, — the stage shown in fig. 6 of Miller's paper. Here instead of the 'sac' described by Miller, the injected specimens show that an extensive plexus is still present. The vessels composing it are larger than in the younger chicks, and Miller has probably figured the largest of these, which in my injections is seen to be continuous with a large lymphatic duct lying next the jugular vein and extending the whole length of the neck. No doubt this is Miller's lymph 'sac' of the seven-day chick.
I have not yet studied this region in chicks older than eight days, but the injections of chicks between seven and eight days confirm Mierzejewski in his descriptions of a 'lymphatic plexus' in contrast to the 'sac' figured by Miller.
I may add that in all the chicks injected between five and onehalf and eight days I was able to demonstrate a connection with the venous system. In the younger chicks (see figure) the connections are more numerous, but subsequently the number is reduced to one or two. I should therefore seriously question Miller's statements in regard to the separation of the sac from the vein and its subsequent reunion with it.
I do not claim that any of my injections, including that shown in the figure, are entirely complete but, as far as they go, they are positive. They reveal the presence of a definite continuous lymphatic plexus in a region where only isolated spaces can be demonstrated by the reconstruction method.
ox A DOUBLE FENESTRAL STRUCTURE IN EMYS
B. W. KUXKKL From the Sheffield Biological Lnhoratory, Yale University
Although the comparative anatomy and development of the sound-transmitting apparatus of reptiles has been extensively studied, the chelonians have received attention in this connection only from Fuchs ('07), Noack ('07), Bender ('11), and very briefly from the present writer ('11). Rathke as early as 1839 observed the continuity of the columella and hyoid arch in snakes. The comparative anatomy of the lacertilian columella auris has been exhaustively studied by Versluys ('03) and was shown by him to be composed of two morphologically distinct parts, a median segment, the stapes, closing the fenestra vestibuli, and a lateral segment, the extracolumella, which remains cartilaginous through life and whose outer end is attached to the tympanic membrane. The independence in origin of columella and otic capsule has not been recognized, however, by all investigators although at the present time the evidence is quite convincing that the columella auris is entirely extra-capsular in origin. In Lacertilia, according to Versluys, the extracolumella apparently takes part in the completion of the hyoid arch and in fact it has been termed the hyostapes by Hoffman ('89) in contradistinction to the otostapes, which that investigator regarded as of labyrinthine origin.
In Testudo, according to Bender ('11), the columella is united with the hyale bj^ means of the interhyale and the extracolumella lies wholly external to the arch which is made up of the cornu hyale, interhyale, and columella. Thus the sound-transmitting apparatus of the chelonians differs from that of the lacertilians,
THE ANATOMICAL RECORD, VOL. 6, XO. 7 JULY, 1912
268 B. W. KUNKEL
principalh' in the relation of the extracolumella to the hyoid arch. That the extracolumella is not a portion of the original arch in the chelonians is evident from the fact that it is, especially in the early stages, considerably behind the other parts of the arch in its degree of chondrification. Later in development, as I have found in Emys lutaria, a processus inter-hyalis, which is as highly chondrified as the extracolumella itself, a d which represents the separate interhyale fused to the extracolumella, may be recognized in certain stages on the medio ventral angle of tTie extracolumella. Regarding the homologies of the columella of the Chelonia, there has been some doubt, as the connection of the same with the hyoid was not established before Bender's recent paper. My own work on Emys which has been extended since my first paper appeared confirms Bender's results on Testudo.
In the present paper I wish to call attention especially to a condition met within several embryonic stages of Emys lutaria, which has not been noted hitherto in the Reptilia, and in which respect Emys resembles the Amphibia. This is the indication of a separate chondrification in the ventral wall of the otic capsule posterior and median to the fenestra vestibuli which is possibly homologous with the operculum of the Urodela. At present it is impossible to confirm the homology absolutely and accordingly I denote it throughout the present paper as stapes inferior.
Kingsbury and Reed ('09) in their extensive work on the columella auris in Amphibia have shown that in the development of the Urodela there are recognized two more or less distinct cartilaginous structures which occupy the fenestra vestibuli, the columella, which possesses a suspensorial connection, and the operculum which lacks the same. The latter segments off from the wall of the capsule itself while the former lies dorsal, or external, and anterior to the latter and develops independently from a center external to the capsule, as Killian ('90) first described in Amblystoma and as was confirmed by Miss Piatt ('97) in Necturus, and by Kingsbury and Reed ('09) in Cryptobranchus, Spelerpes, and Plethodon. The columella typically possesses a stilus which extends laterally from the fenestra vesti
DOUBLE FENESTRAL STRUCTURE IN EMYS 209
l)uli Ix'tweon the vena capitis lateralis above and the arteria earotis intern.i below. Tiie relation of the stilus to the nervus facialis is somewhat variable . among the Amphibia although King-bury ('03) has shown that this relationship of nerve and eoluniella is not of fundamental importance in establishing the homology. In Xecturus, Proteus, and Typhlomolge, the ramus jugularis nervi facialis pas.ses above the stilus while in all the other forms in which a stilus is present, the nerve lies ventral to it. In Emys the columella passes ventral to the entire hyomandibular trunk and not to only a part of it as is the case in the Urodela. This, however, does not seem to be an important difference between the columellae of the tw^o groups. Besides this, its origin external to the otic capsule, its position ventral to the vena capitis lateralis and dorsal to the arteria earotis interna, po lit toward the morphological similarity of the two. The relations of the external end of the columella, however, offer some difficulties. In Emys th'^ columella is connected with an extracolumella and an interhyale, the latter of which Bender has shown connects it with the hyoid arch. In addition to this the extracoluinella is continuous anteriorly and dorsalh' with the quadratum in early stages. In the Urodela, on the other hand, according to Kingsbury and Reed, the primary relationship of the lateral end of the columella is with the squamosum, an extracoluinella not being present.
The structure w^hich I designate as stapes inferior in Emys agrees with the operculum of the Urodela in: (a) its relation to the fenestra! plate of the columella, (b) its origin from the otic capsule, (c) its tendency to be confluent with the otic capsule caudalh', and (d) its relation at an early stage to the ductus perilymphaticus. Kingsbury and Reed on page 605 give as the criteria of the operculum in Urodela its "lack of connection with the skeleton outside of the ear capsule and the attachment of ]\I. opercularis." The absence of this muscle in theChelonia prevents the application of this second criterion.
At the earliest stage which I have studied, in which the imperfectly difTerentiated carapace measured about 4.7 mm. in length, the cartilages of the skull are laid down in the most advanced
270 B. W. KUNKEL
portions simply as early prechondrium. At this stage the otic capsule is represented by a mass of mesenchyme in which the matrix characteristic of prechondrium is not yet present, although the nuclei are somewhat crowded together, as occurs in undifferentiated mesenchyme before chondrification takes place. The process of chondrification apparently begins at a point toward the posterior end of the capsule in the region immediately dorsal and posterior to the future fenestra vestibuli, surrounding the external opening of the canalis glossopharyngeus in which the nervus glossopharyngeus lies in its passage through the otic capsule. In its dorsal and median portions, the capsule is imperfectly marked off from the surrounding mesenchyme. The connection of the capsule with the planum basale does not extend in front of the nervus facialis. An earlier stage in which the separation between these two parts is complete was not available in the series studied although there are indications of this in my youngest specimen (fig. 1). The fusion apparently begins somewhat posterior to the middle of the capsule and extends more rapidly anteriorl}^ than posteriorly.
In my youngest embryo the columella exhibits a much more advanced stage of chondrification, especially at its lateral end, than the otic capsule. Its median end presses slightly against the lateral wall of the cochlear portion of the capsule at a point corresponding to the future fenestra vestibuli which has not yet formed (fig. 2) . In this and the succeeding, stage the more advanced chondrification of the columella is quite distinct from that of the capsule. The extracolumella is composed of a mass of less highly differentiated mesenchyme which is situated at the lateral end of the columella and is continuous anteriorly and dorsally-with the blastem of the palatoquadratum. On the outside of the body it is evident as a strong convexity immediately ventral to the external opening of the hyomandibular cleft (fig. 2). Midway between the distal end of the columella above and that of the hyoid arch below, and so completing the curve between these two parts, is the interhyale. * This has the form of an ovoid mass of prechondrium (fig. 3), as Bender has already shown. The columella auris and interhj^ale are to be
DDlHLi: FENESTRAL STRUCTURE IN EMYS
(i.c.r., artciia rarotis conmuiiiis
tt.c.i., arti'iia carotis interna
c.b., crista basijjteiypoidi'a
C.C., caviini cochloae
ch.d., chorda dorsalis
col., cohnnclla auris
("./»., crista parotica
c.s.t.. canalis semicircularis lateralis
c.t., chorda tj'mpani
(/./>., ductus pcrih'mphaticus
/./)., foramen anteriiis spino-occipitale
f.m., fissura metotica
g.a., ganglion acusticum
g.g., ganglion glossopharyngeum
g.gen., ganglion geniculi
Udi., ineiuhraiious iabyrintli
M.c, Mockel's cartilage
0., stapes inferior
ol.cap., otic capsule
p.b., planum basale
q., quadrat um
r.s.L, recessus scalae tympani
v.c.L, vena capitis lateralis
/., first branchial cleft
]'//, ramus hyomandibularis nervi
facialis VII~IX, ramus communicans nervi
facialis ad nervum glossopharyn geum
VIII, nervus acusticus
IX, nervus glossopharyngeus A' , nervus vagus
Fig. 1 Transverse section of an embryo having a carapace-length of 4.7 mm., through the ventral portion of the otic capsule in front of columella auris, showing the line of union between planum basale and otic capsule. X 200.
B. W. KUNKEL
looked upon as derivatives of a previously continuous hyoid arch lying between the first and second visceral clefts. The extracolumella, according to Bender, is a secondary addition to the most lateral portion of the hyoid arch. In respect, then, to the relation of columella, extracolumella, and hyoid, there is essential agreement between the Chelonia and Lacertilia.
The relation of the nerves and blood vessels to the structures in question is the same as was described by Noack ('07). The vena capitis lateralis is a large vessel which extends lateral to the otic capsule immediately dorsal to the ganglion vagi posteriorly and lodged in the shallow groove which marks the lateral
Figs. 2 and 3 Transverse sections through the otic capsule of an embryo having a carapace-length of 4.7 mm. The section in fig. 3 is 105m posterior to that of fig. 2. X 40.
surface of the capsule ventral to the prominentia canalis semicircularis lateralis. The arteria carotis interna lies ventral and lateral to the otic capsule and is separated from the aforementioned vein \^y the columella auris. The ramus hyomandibularis n. facialis extends in a posterior direction from the ganglion geniculi alongside of the otic capsule and dorsal to the columella. At the level of the columella, or immediately behind it, the chorda tympani is given off in a horizontal direction laterally. This branch then bends forward and ventrally to the mandible. After giving off the chorda tympani, the ramus hyomandibularis continues posteriorly and gives off the ramus communicans n.
Dor HI, K FKXKsrKAL STRUCTURE IN EMYS 273
facialis ad ^lossophai^Nii^ciun and tlicii heiids ventrally to Ihc imisclrs which it supplies.
At ji hiter stage (an embryo witli a carapace-length of o.'i nun.) wiiMi chondrification has progressed further, the fenestral plat(> of the columella comes to rest against the lagena so that the fenestra vestibuli is already formed although the fenestral plate tills it completely. The distinction between the fenestral plate and the capsular wall becomes more pronounced with age on account of the relatively greater rapidity of chondrification of the columella. Anteriorly and ventrally, as well as anterodorsally, there is a distinct line of demarcation between the capsular wall and the fenestral plate although postero-dorsally there is a more gradual transition between the two structures. Immediately medial to the ventral margin of the fenestral plate and forming the floor of the lagenar portion of the capsule is a space which is quite distinctly marked off from the lateral margin of the planum basale on the one hand and the columella on the other. This area is characterized by its cells with smaller nuclei crowded together in contrast on the one hand to the larger and more widely separated ones of the planum basale which also exhibit a concentric arrangement, and on the other to the more advanced chondrification of the fenestral plate of the columella.
The condensed mesenchyme filling this space between the fenestral plate and the planum basale is somewhat anterior to the future stapes inferior which has not yet become differentiated. From the lateral margin of this space and extending nearly as far posteriorly as the fenestral plate of the columella is a distinct ridge which represents the crista basipterygoidea projecting ventro-laterally above the arteria carotis interna.
At the next stage (an embryo having a carapace-length of 7 mm.) the relation of these parts is essentially the same as has been described, but because of the more advanced stage of chondrification the boundaries of the various cartilages are more distinct. There are, however, several changes worthy of note.
The otic capsule becomes continuous with the planum basale by both a pre- and postfacial commissure. The lateral margin
B. W. KUNKEL
of the planum basale extends freely as a ventro-laterally projecting ridge of less highlj'- differentiated prechondrium, the crista basipterygoidea, which in passing posteriorly toward the region of the foramen faciale becomes separated from the planum
Fig. 4 Transverse section through the otic capsule of an embryo having a carapace-length of 5.2 mm., showing the extension of the fenestral plate of columella dorsally and the crista basipterygoidea. X 40.
Fig. 5 Transverse section through the otic capsule of an embryo having a carapace-length of 8 mm., showing the relations of columella, stapes inferior, first branchial cleft, and extracolumella. X 40.
basale and continues as a longitudinal rod parallel to the. lateral margin of the planum basale and connected with it by a mass of dense mesenchyme (fig. 22). Posteriorly this ridge comes to lie more nearly horizontally and in the region immediately in front of the columella it fuses with the floor of the otic capsule which is here quite distinctly separated from the planum basale (fig. G).
Figs. 6 to 13 A series of transverse sections through the posterior portion of the otic capsule of an embryo having a carapace-length of 7 mm. The crista basij)terygoidea terminates in front of the stapes inferior. The columella extends medially against the membranous labyrinth and lies ventral to the vena ca[)itis lateralis and ramus hyomandibularis nervi facialis and dorsal to the arteria carotis interna and ramus communicans nervi facialis ad nervum glossopharj'ngeum. In fig. 10 the columella and stapes inferior are seen alongside of eachother, while caudal to this section (fig. 11, et seq.) only the latter structure is visible. X 40.
'"•' Hl-K 1-ENESTRAL STItUCTUUK IN EMYS
1 M. .
~a c. c.
276 B. W. KUNKEL
The floor of the capsule, beginning a short distance in front of the cohunella is demarcated from the planum basale by being less highh^ chondrified than the latter, as in the previous stage, and by being constricted off from it by a shallow groove on its ventral side. Further caudally the constriction disappears and the chondrification exhibits further development so that the planum basale apparently extends as far as the ventral margin of the fenestral plate of the columella. From the outer margin of this plate of younger prechondrium the posterior end of the crista basipterygoidea extends in a horizontal direction immediately beneath the columella where it disappears (fig. 6) . A few sections behind the end of the crista basipterygoidea, the capsular wall immediately ventral to the fenestral plate of the columella exhibits a retarded chondrification and further caudally becomes segmented from the planum basale (fig. 10) resembling closely the operculum of the urodelan otic capsule. The stapes inferior at this stage is somewhat lens-shaped with the ventral edge in front thicker than the dorsal margin. Further caudally it becomes symmetrical. It lies with its median face close against the lagena immediately ventral and posterior to the columella'. Accordingly, it has a position slightly inclined to the vertical. It rests with its ventral edge upon the floor of the capsule which is joined medially to the lateral margin of the planum basale and differentiated from it by its younger condition. Posteriorly and dorsally it becomes confluent with the wall of thg capsule, while ventrally it remains quite distinct from the condensed mesenchyme lying between it and the planum basale.
Posterior to the stapes inferior the ventro-lateral capsular wall rolls over medially at its ventral edge to form a kind of trough in which the most posterior portion of the sac cuius rests (fig. 13). Its free median edge is separated by a narrow space from the median wall of the capsule in which space the first trace of the ductus perilymphaticus is seen (figs. 12 and 13).
The ventro-lateral wall of the capsule, which is continuous with the stapes inferior, therefore comes to lie interposed between the lagena dor.-ally and the mass of condensed mesenchyme
DOUBLE FENESTKAL STRUCTURE IN EMYS
veiitrally wliicli further forward forms the floor of the capsule. A few sections further hack (fig. 24) the portion of the capsular wall wiiicii is continuous anteriorly with the stapes inferior is seen ventral to the nervous glossopharyngeus and dorso-latcral to the recessus scalae tynipani within which a j)ortion of the ductus perilymphaticus lies.
The mass of tissue lateral to the planum basale and ventral to the stapes inferior is apparently formed from the mesenchyme of the surrounding regions by actual condensation. It extends
Figs. 14 to 21 Transverse sections through the posterior portion of an embryo having a carapace-length of 9 mm. showing the relation of nervi glossopharyngeus and vagus, ductus perilymphaticus, columella, and stapes inferior. The sections are in order from posterior to anterior. X 20.
beyond the external surface of the neighboring cartilages as if overflowing and spreading around their margins (fig. 12); still further posteriorly at the extreme anterior end of the fissura metotica, this mass of condensed mesenchyme forms a kind of knob projecting from the lateral margin of the planum basale in a dorso-lateral direction and apparently partially occluding the fissure from its anterior end and enclosing below and on the side the recessus scalae tympani. The musculus collocapitis brevis is evident at this time simply as a mass of much
B. W. KUNKEL
concentrated tissue occupying the ventro-lateral angle of the planum basale and stretching caudally.
In an embryo having a carapace-length of 8 mm. the stapes inferior is still separate from both the planum basale and the otic capsule. The fenestral plate of the columella is well separated from the margins of the fenestra especially along its ventral margin, but even along the upper margin where the continuity between the fenestral plate and the capsule is more apparent, the differentiation is appreciable (figs. 14-21). On the ventral
OO 0^5 0<J^o°4'g-3p•■S**-■
Fig. 22 Transverse section of an embryo having a carapace-length of 7 m^n. showing* the separation of the planum basale and crista basipterygoidea. X 200.
Fig. 23 Transverse section through the floor of the otic capsule of an embryo having a carapace-length of 8 mm. showing the anterior end of stapes inferior, crista basipterygoidea, and columella. X 200.
side of the fenestral plate there is a wide gap between it and the stapes inferior (fig. 5).
The crista basipterygoidea at this stage has grown further caudally beyond the front margin of the columella as a cylindrical rod, and is separated sHghtly from the capsule, lying lateral to the dorsal margin of the stapes inferior (fig. 5), which has extended itself further anteriorly than in the previous stage.
The stapes inferior at this stage exhibits on its inner surface a decided convexity so that it is strongly lens-shaped, but because its upper margin is thinner than the fenestral plate there is left a recess between it and the fenestral plate (fig. 19).
DOUBLE rF:NESTHAL STUUCTURE IN EMYS 271)
After this stage of developinent is reuched the stapes inferior apparently fuses indistinguisliahly with the otic capsule and its identity is lost.
In suminin"- up, then, the results of this paper there is, at certain stages of development of p]niys lutaria, a segmentation
Fig. 24 Transverse section through the posterior end of the ventral portion of the otic capsule of an embr^-o having a carapace-length of 7 mm. This section is the most posterior of the series of sections in figs. 6 to 13. The section shows the relation of nervus glossopharj'ngeus, otic capsule, recessus scalae tympani and fissura metotica. X 40.
of the wall of the otic capsule in the region immediately ventral, or medial, to the fenestral plate of the columella which forms a plate that is continuous caudally with the capsule and at an early stage lies lateral to the ductus perilj^nphaticus, as has been described for the operculum in Urodela.
Bender, O. 1911 Ueber Herkunft und Entwickelung der Columella auris bei Testudo graeca. Anat. Anz. Bd., 40, pp. 161-177.
FucHS, H. 1907 Ueber die Entwickelung des Operculums der Urodelen und des Distelidiums ("Columella" auris) einiger Reptilien. Verhandl. d. anat. Gesellsch. zu Wiirzburg, pp. 8-31.
Gaupp, E. 1899 On^ogenese und Phylogenese des schallleitenden Apparates bei den Wirbeltieren. Ergebn. d. Anat. u. Entwickelungsgesch, Bd. 8, pp. 990-1149.
1905 Die Entwickelung des Kopfskelettes. Hertwig's Handbuch d. Entwickelungslehre, Bd. 3, pp. 57.3-874.
280 B. W. KUNKEL
Hoffman, C. K. 1898 Ueber die morphologische Bedeutung des Gehorknochelschens bei den Reptilien. Zool. Anz., Bd. 12, pp. 336-337.
1890 Schildkroten. Bronn's Klassen u. Ordnungen, Bd. 6, Abt. 3, pp183-217.
KiLLi.\N', G. 1890 Die Ohrmuskeln des Krokodils nebst vorlaufigen Bemerkungen fiber die Homologie des Musculus stapedius und des Stapes. Jen. Zeitschr. f. Naturwissensch. Bd. 24, pp. 634-654.
Kingsbury, B. F. 1903 The columella auris and nervus facialis in the Urodela. Jour. Comp. Near. vol. 13, pp. 313-334.
Kingsbury, B. F. and Reed, H. D. 1909 The columella auris in Amphibia. Jour. Morph., vol. 20, ppv 549-628.
KuNKEL, B. W. 1911 Zur Entwickelunsgechichte und vergleichenden Morphologie des Schildkrotenschadels. Anal. Anz. Bd. 39, pp. 354-364.
No.\CK, 1907 Ueber die Entwicklung des IMittelohres von Emys europaea nebst Bemerkungen zur Neurologic dieser Schildkroten. Arch. f. mikr. Anat., Bd. 69, pp. 457-490.
Platt, Julia 1897 The development of the cartilaginous skull and of the branchial and hypoglossal musculature in Necturus. Morph. Jahrb., Bd. 25, pp. 377-464.
Rathke, H. 1839 Bemerkungen i'lber die Entwickelung des Schadels der Wirbeltiere. 4te Bericht iiber das naturwissenschaftliche Seminar bei der Universitat zu Konigsberg.
1848 Ueber die Entwickelung der Schildkroten. Braunschweig.
Versluys, J. 1903 Die Entwicklung der Columella auris bei den Lacertilien. Ein Beitrag zur Kenntniss der schalUeitenden Apparate und des Zungenbeinbogens bei den Sauropsiden. Zool. Jahrb. Abt. f. Anat., Bd. 19. pp. 107-188.