Proceedings of the Association of American Anatomists V 



In the lower jaw are two cartilaginous elements, the well-known 

 Meckel's cartilage and a second very large cartilage lying outside the 

 posterior part of the Meckelian and extending downward to form the 

 angle of the definitive jaw and upwards to fonn the condyle for articula- 

 tion with the glenoid fossa of the squamosal. This condyloid cartilage, 

 which ossifies by endochondrostosis, the author, like Parker, would 

 homologise with the lower labial cartilage of the elasmobranchs which can 

 be traced upwards at least as far as the ganoids, where it occurs in 

 Polypterus (Van AA'ijhe) and Amia (Allis). In front this condyloid 

 bone becomes confluent with the dentale, a membrane bone arising on the 

 external surface of the Meckelian cartilage. On its anterior-superior 

 margin is a second membrane bone, the coronoid, which forms the 

 coronoid process of the upper jaw. On the inner side of the dentale 

 occurs a third membrane bone in the position of the splenial of the 

 lower vertebrates, while the inner alveolar margin of the anterior end of 

 the dentale may prove to be the prosplenial, but this point has not ^^et 

 been decided. The articulare is, as has been pointed out in a previous 

 paper on the ossicula auditus, to be found in, a part of the malleus, to 

 which a distinct membrane bone, the angulare, also contributes. 



NOTES ON THE ORIGIN OF THE CAROTID GLAND AND THE MORPHO- 

 LOGICAL COMPARISON OF THE TRIGEMINAL AND FACIAL 

 NERVES IN MAMMALIAN EMBRYOS. By Henry Fox. The Temple 

 College, Philadelphia. 



According to one view, the carotid gland arises by a thickening of 

 the walls of the capillaries derived from the carotid artery; according to 

 another view, which receives its strongest support in the careful investi- 

 gation of Prenant, the organ arises from the endoderm of the third 

 pharyngeal pouch. The author's investigations support the latter view. 

 In a pig embryo of 9 mm., the gland appears as a series of blind follic- 

 ular outgrowths from the anterior wall of the third pharyngeal pouch. 

 By the study of several succeeding stages, these outgrowths Avere traced 

 into the definitive carotid gland of later stages. Similarities in structure 

 in the case of the trigeminal and facial nerves are strikingly brought out 

 in the study of early pig embryos. The trigeminal nerve bears the 

 same relation to the mouth (stomatodeum) that the facial does to the 

 first pharyngeal pouch. The Gasserian ganglion lies above the angle of 

 the mouth; the geniculate, above the first pharyngeal pouch. Each 

 ganglion gives off two nerves, one of which passes in front of the cor- 

 responding pouch, the other behind it. The former corresponds to the 

 pretrematicus of lower vertebrates; in the mammals it becomes the 

 superior maxillary nerve in the case of the trigeminal ; in the case of 



