The Pharyngeal Pouches in the Mammalia 247 



Fig. 52. — Part of a transverse sectiou of the bead of a 36 mm. pig, showing 

 relation of the external auditory meatus. E. Au., to the tympanic pouch, 

 prom., promontory of the tympanic pouch; the projection below the manu- 

 brium is the post-manubrial ridge. X 50, reduced %. 



Fig. 53. — Transverse section through carotid gland and adjacent part of 

 third pouch. Pig, 13 mm., M\ x 300 circa, reduced %. 



Fig. 54. — Cross section of a glandule thyroidlenne in a 20 mm. pig. Har- 

 vard medical collection, x 300 circa, reduced i/^. 



Fig. 55. — Ventral view of the pharyngeal region of cat of 4.6 mm., No. 398, 

 Harvard medical collection, showing associated blood-vessels. St., stomato- 

 deum ; v. v., vitelline veins ; x., opening of enteron into yolk sac. X 50, 

 reduced %. 



Fig. 56. — Lateral view of the same region, x 50, reduced %. 



Fig. 57. — Lateral view of the pharyngeal region in a cat. No. 413, Harvard 

 medical collection, showing pharynx and associated aortic arches. M. Gr., 

 median oral groove ; Ph. P. 1-3, first to third pharyngeal pouches. X 80, 

 reduced i/^. 



Fig. 58. — Lateral view of the pharynx in a 6.2 mm. cat, No. 380, Harvard 

 medical collection. Ton. F., antero-lateral border of the second pouch, in later 

 stages the tonsillar sinus, x 60, reduced %. 



Fig. 59.^ — Dorsal view of the pharynx in the same cat, showing also the 

 related ectodermal parts. S. Pc, sinus prnecervicalis ; F. Pc, fundus priBcer- 

 vicalis. X 60, reduced 14. 



Fig. 60. — Ventral view of the pharyngeal region in the same cat. X 60, 

 reduced V-2. 



Fig. 61. — Ventral view of the pharyngeal region in a 9.7 mm. cat, No. 446, 

 Harvard medical collection. On the right the plane of section is higbe) 

 than on the left side. SM. F.. submeckelian fold, barelj^ visible at this stage ; 

 on the right the interior of the sinus prtecervicalis is shown ; Tub., tubercuhua 

 impar ; V. F., vestibular fold. X 60, reduced %. 



Fig. 62. — Region of the sinus prjiecervicalis in the same cat. F. Pc, fundus 

 pi'fecervicalis ; Ph. P. 4, fourth pharyngeal pouch, only its outer tip showing on 

 the left side ; V. D. 2-3, ventral diverticula of second and third pouches, their 

 inferior parts cut off ; V. Pc, vesicula prtecervicalis. X 80, reduced i/^. 



Fig. 63. — Lateral view of the pharynx in a 15 mm. cat, No. 436, Harvard 

 medical collection. Mn. f., manubrial fossa ; P. S. F., post-salpingeal ridge ; 

 S. Pi., sinus piriformis ; V. M. R., ventro-mesial border. X 60, reduced Vs- 



Fig. 64. — Dorso-posterior view of pharynx in the same animal. The figure 

 shows the initial separation of the tympanic pouch and tonsillar fold, 

 p s. f., postsalpingeal ridge; s. t. p., sulcus tympanicus posterior; ton. f., 

 tonsillar fold ; v. m. r., ventro-mesial border ; z., incision between tympanic 

 pouch and tonsillar fold. X 30, reduced %. 



