OSSICULA AUD1TUS IN THE HIGHER MAMMALIA. 
923 
primitive jugular vein, facial nerve, hyoidean cartilage in the 
whole of its length (partly in outline), mandibular branch of 
seventh, anterior crus of stapes, part of neck of malleus, basis 
cranii, sulcus tubo-tympanicus, arteria stapedio-maxillaris, 
thyro-hyoid cartilage (cartilage of first branchial arch), and 
thyroid cartilage. 
Fig. 24. Nearly horizontal section, showing chorda dorsalis, investing 
mass, one of the cervical vertebrae, with vertebral artery, 
arteria carotis communis, arteria carotis interna, arteria 
stapedio-maxillaris, periotic capsule, stapes, incus, hyoidean 
cartilage, facial nerve, glosso-pharyngeal, pneumogas trie, spinal 
accessory and hypo-glossal nerves, and gasserian ganglion. 
Figs. 25-28. Sections from embryoes 1*3 centim. in length. 
Fig. 25. Longitudinal vertical section, showing cartilages of mandibular 
and hyoidean arches, the various parts of malleus and incus, 
facial nerve with its mandibular (chorda tympani) branch and 
external auditory meatus. 
Fig. 26. Transverse vertical section, showing malleus, sulcus tympanicus, 
throat cavity, meatus auditorius externus, periotic capsule, 
arteria carotis interna, gasserian ganglion, ganglion of facial, 
hyoidean cartilage, and basis cranii. 
PLATE 57. 
Fig. 27. Transverse vertical section, from the same series as preceding 
figure, but through a plane more posterior, showing incus and 
stapes, arteria stapedio-maxillaris, arteria carotis communis, 
arteria carotis interna, periotic capsule, basis cranii, hyoidean 
cartilage, and mandibular branch of seventh nerve. 
Fig. 28. Transverse vertical section through a plane posterior to fig. 27, 
showing periotic capsule with primitive gap for fenestra 
rotunda, facial, glosso-pharyngeal, and pneumogastric nerves, 
basis cranii, cervical vertebrae, and primitive jugular vein. 
Figs. 29-30. Sections from embryoes 2 centims. in length. 
Fig. 29. Transverse vertical section, showing head, neck, and manubrium 
of the malleus, tensor tympani muscle, basis cranii, periotic 
capsule, gasserian ganglion, ganglion of the facial, meatus 
auditorius externus, and sulcus tympanicus. 
Fig. 30. Transverse vertical section through a plane posterior to fig. 29, 
showing incus and stapes, with arteria stapedio-maxillaris. 
Figs. 31—38. Sections from embryoes nearly 4 centims. in length. 
