DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 275 



from a keel of proliferation attached to the epithelium of the alveo- 

 lingual region, at a small but perfectly distinct interval, lateral to the 

 Ungual sulcus. At no time has it any contact with the subn.axiUary, 

 but is from its inception and throughout its development an absolute y 

 independent element. Both glands are estabhshed first m the nagh- 

 borhood of the submaxillary ganglion, and subsequently extend 

 craniad along the lingual sulcus and the floor of the alveolmgual region, 

 following their separate lines at somewhat different rates, but so tha. 

 the submaxillary is always in advance of the greater subhngual. At a 

 late period (embryo of 70 millimeters) the lesser subhngual series is 

 represented bv a few sprouts in the caudal portion of the furrow, which 

 forms the lateral boundary of the plica subUnguahs, the homologue 

 of which in man is the site of the early members of this series (Rivmian, 

 glands, glandule sublinguales minores). Three independent glandif- 

 erous Unes are thus distinguishable, a mesal, mtermediate and 

 lateral, yielding, respectively, the submaxillary, greater sublingual, and 

 lesser ;ubhngual glands, and in the order named. The cat present 

 the glands of this region, not indeed in their lowest terms, for all three 

 lines are represented, but in a schematically simple form The devel- 

 opmental process, in contrast to that of the buccal sulcus series, is 

 also remarkably uniform and fixed. 



THE SUBMAXILLARY GLAND 



The lingual sulcus, as has been said, appears in separate segments, 

 one craniad in what is subsequently the frenular region, -d one near 

 the submaxillary ganglion. The intermediate region of the uku 

 is at first represented only by a rounded angle, where the epithelium of 

 the tongue meets that of the floor of the alveolingual region (Figs. 22-24) 

 which gradually becomes acute (Fig. 1 22), without attaining any depth 

 or havTng parallel walls. This condition is attained m the majority of 

 embryos of 15 millimeters, but the intermediate segment tends to be shal- 

 lower than the more cranial and caudal portions of the sulcus. In a 

 few cases, on the other hand, it never becomes more than an angle or 

 may even be entirely absent in embryos of 18 to 19 m^H^eters. Th. 

 faci it will be seen, has some importance in determining the nature of 

 the process, which gives rise to the submaxillary duct. 



