THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 29 



and ma} accordingly be designated, massa sublingualis, sublingual 

 mass. Its components are the constant Rivinian elements, glandulce 

 sublinguales minores, lesser sublingual glands ; the inconstant Bartho- 

 linian gland, glandula sublingualis major, greater sublingual gland ; 

 and finally variant lobules of the submaxillary draining into the venter 

 of the duct, which on comparative grounds Huntington has designated 

 ventral accessory submaxillaries. 



It is convenient to divide the salivary glands for purposes of de- 

 scription into those of the vestibule and those of the cavum oris proprius. 

 In order to secure as continuous an account of the development of 

 the several elements as the material permits, the embryos have been 

 arranged solely with reference to the degree of development of the 

 glands under consideration, and as this is subject to some variation of 

 rate, there are a few departures from chronological order in the series. 

 Descriptions of three embryos of the Columbia Collection have been 

 inserted. 



THE GLANDS OF THE VESTIBULE 



It may facilitate the interpretation of this discontinuous and scanty 

 series of human embryos if a brief summary of the findings in the 

 domestic cat be prefixed. In a large, and for the early stages, com- 

 plete series of these embryos it was possible to follow step by step the 

 formation of the derivatives of the buccal sulcus. The sulcus in 

 embryos of 9-10 millimeters presented a continuous thickening of 

 its epithelium along the fundus, thinning mesad along its ventral and 

 dorsal walls. Out of this continuous anlage a cylinder of cells was 

 formed by a process of folding and constriction. Ultimately it is 

 widely displaced from the oral epitheUum and comes into close contact 

 with the ental surface of the muscles of mastication, where it persists 

 until the stage of 70 milhmeters, the oldest embryo as yet examined. 

 This element has been termed the orbital inclusion because of its deri- 

 vation from a segment of the buccal sulcus which subsequently in the 

 cat gives rise to the orbital glands, and because of its ultimate com- 

 plete separation from the oral epithehum and inclusion in the mesen- 

 chyme. The folding begins caudad at the level of the mandibular 

 nerve and spreads craniad from that point involving an increasing 



