138 PRIMATE ALVEOLINGUAL SALIVARY AREA 



majority of the individuals composing the genus, but which, at 

 one time in the course of normal development, was equally avail- 

 able to all. It would not be difficult to reason from these findings 

 far forward along the line of future speciahzation to a point in the 

 cat's vascular development where the at present unlimited choice of 

 axial venous pathways becomes reduced ontogenetically to a degree 

 permitting only limited selection of vascular lines for further develop- 

 ment into adult conditions. With the attainment of this stage the 

 cat would, in this department of its venous system, possess far greater 

 "fixity of type" than it at present enjoys. 



If we translate these findings to the entirely different field of alveo- 

 Ungual glandular development, then it becomes apparent, from our 

 knowledge of the development of these structures in man and in some 

 of the lower mammalia, that the mammaUan embryo, if it ever phylo- 

 gejietically retained an unHmited choice for the selection of special Unes 

 of glandular development, no longer enjoys the liberty. 



There is some ontogenetic e\'idence. as previously stated, that a 

 more liberal and comprehensive groundplan formed the basis for the 

 evolution of the present embryonal and adult tj^pes of alveoHngual 

 salivary organization. But in general the mammahan salivary glands 

 of this region develop in each individual along ontogenetic lines which 

 are definite and limited from the period of their first appearance up to 

 the accompUshment of the final result. 



Notwithstanding these facts, we are confronted in the adult with a 

 very considerable range of individual variation. 



Man is, at present, the only primate available for the purpose of 

 determining this variant range in the adult. In him we encounter 

 three perfectly distinct adult t^pes in the relation of the subma.xil- 

 lary Une to a possible intermediate element, the greater sublingual 

 gland and its duct, and to the lateral group of separate and distinct 

 glandular elements which form the division of the "alveoHngual 

 glands'" or of the lesser subhngual glands. This analysis is entirely 

 independent of the comphcations introduced into the interpretation 

 of the adult human "massa sublingualis" by the incorporation into 

 the same of elements derived from the submaxillary line by the- 

 development of "accessory" or "secondary" submaxillary com- 

 ponents. ' 



