OSSICULA AUD1TUS IN THE HIGHEE MAMMALIA. 
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gasserian ganglion, primitive jugular vein, facial nerve, with 
its mandibular (chorda tympani) branch, mouth cavity, and 
sulcus tympanicus. 
Figs. 8—'9. Sections of Pig embryoes 2 centims. in length X 25. 
Fig. 8. A stage later than fig. 5. 
Fig. 9. A stage later than fig. 7. Shows in addition the cochlear and 
vestibular divisions of the ganglion acusticum. 
PLATE 55. 
Fig. 10. Longitudinal vertical section of Pig embryo 2*6 centims. in length X 25, 
showing the cartilages of the first two post-oral arches, the periotic capsule 
with the semicircular canals, and the facial nerve with its mandibular 
(chorda tympani) branch. 
Figs. 11-12. Sections of Human embryo fully 1 centim. in length X 25. 
Fig. 11. Longitudinal vertical section, parallel to the middle line of the 
head, showing maxillary and mandibular branches of the fifth 
nerve, facial nerve with its mandibular (chorda tympani) 
branch; outlines of the ganglia of the fifth and seventh; and 
mandibular and hyoidean cartilages. 
Fig. 12. Transverse vertical section showing basis cranii, carotis interna, 
arteria stapedialis, periotic capsule, stapes, hyoidean cartilage, 
ganglion and trunk of facial, and ganglion gasserii. 
Figs. 13-16. Sections of Human embryo 4 centims. in length X 25. 
Fig. 13. Transverse vertical section showing periotic capsule, occipital 
and hyoidean cartilages, tympanic annulus, sulcus tympanicus, 
meatus auditorius externus, facial nerve, head, neck (with 
processus muscularis of Hyrtl), and manubrium of the 
malleus, and tensor tympani muscle. 
Fig. 14. Transverse vertical section, through a plane posterior to that 
of fig. 13, showing head and long crus of the incus, and stapes, 
no artery (which has disappeared). 
Fig. 15. Longitudinal vertical section, showing mandibular and hyoidean 
cartilages, head, neck, and manubrium of the malleus, incus, 
tympanic annulus and sulcus tympanicus. 
Fig. 16. Longitudinal vertical section, showing part of mandibular 
cartilage, incus (body and crura), periotic capsule, hyoidean 
cartilage undergoing segmentation, facial nerve with chorda 
tympani (mandibular) branch, manubrium mallei, with processus 
muscularis and tensor tympani muscle, sulcus tympanicus and 
tympanic annulus. 
6 b 2 
