I go DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 



the earliest of the derivatives of the buccal sulcus. It has been termed 

 the orbital inclusion, because it is derived from a segment of the sulcus 

 which later gives origin to the orbital glands, and because in its sub- 

 sequent development it separates from the oral epithelium and be- 

 comes embedded in the mesenchyme along the ental surface of the 

 masseter and internal pterygoid muscles. 



The roof of the mouth ental to the buccal sulcus presents a well- 

 defined convexity, the rudiment of the palate process, which dimin- 

 ished craniad attains its maximum in the mandibular plane, and may, 

 therefore, in part at least, owe its inception to the confining influence 

 of the mandibular nerves. These do not retain their primitive 

 relation to the buccal sulcus. Gradually they undergo a relative 

 displacement caudad toward the fauces. Their place is taken by 

 the anlages of the muscles of mastication, which occupy the region 

 between the buccal sulcus and the first pouch, and continue to 

 present an obstacle to the expansion of the caudal portion of the 

 oral cavity. 



The floor of the mouth still presents distinctly three sagittal ridges, 

 the tuberculum impar and the maxillary convexities, or the lateral 

 tongue swellings (seitUche Ziingenwiilste) of Kallius. The latter have 

 increased and seem to be displacing dorsad the tuberculum impar, 

 which has remained approximately of the same size (Fig. lo). From 

 this time the tuberculum impar begins to lose its identit)' and become 

 more and more blended with convexities of the mandibular processes. 

 In an embryo of 10.5 miUimeters it forms a sUght crest along the 

 midUne of the elevation produced by their fusion (Fig. 11). The time 

 of its ultimate disappearance varies. It is lost in the 11.5 millimeter 

 embryos of our series; on the other hand, in the 13.5 millimeter em- 

 bryo. No. 189, it is still recognizable (Figs. 36-39). 



The formation of the cranial segment of the tongue here conforms 

 to the description given of it by KalUus for reptiles, and by Hammar 

 for man, and contains both the lateral anlages of Born and the tuber- 

 culum impar of His. The caudal and cranial segments of the tongue 

 thus agree in composition, ha\'ing the same components, the ventral 

 ends of visceral bars and median copular elements. That the tuber- 

 culum impar is a copular element seems given by its position, inter- 

 posed as it is between the extremities of the mandibular and hyoid 



