PRIMATE ALVEOLINGUAL SALIVARY AREA 133 



elements employed, the patterns of Figs. 7 and 8 might have been 

 changed to those shown in Figs, ga and gb, which represent one of 

 the most complex and highly developed types encountered in the 

 entire adult mammalian series. The preceding examples may suffice 

 to suggest the inherent possibihties in glandular combinations. 



II. Mechanical Factors in the Formation and Relations of 

 . THE Oral Floor influencing Alveolingual Glandular De- 

 velopment 



In applying the preceding strictly hypothetical genetic considera- 

 tions to the interpretation of the adult mammalian types, it becomes 

 evident that development is greatly influenced by the mechanical 

 conditions imposed on a uniform potential glandiferous field in the 

 alveohngual region and its immediate environment. The area of the 

 oral floor bounded mesad by the elevation of the tongue, creating the 

 lingual sulcus, and laterad by the vertical projection of the mandible 

 along the alveolar sulcus, suffers in the first place a reduction of its 

 available coronal diameter in proceeding cephalocaudad. This is 

 primarily due to three factors : — 



(a) The space occupied by the tongue proper on the oral floor in 

 the interval between the alveolingual gland areas steadily increases in 

 transverse measure in the cephalocaudal direction. 



(b) The caudal portion of the alveohngual area is further narrowed 

 from the sides by the prominence of the ramus and the internal ptery- 

 goid muscle, and from above by the anterior faucial fold and the con- 

 tained palatoglossus muscle. 



(c) The Ungual nerve, in acceding to the lateral border of the tongue, 

 comes, in primates, into close and intimate relations with the oral 

 mucosa and the lateral alveolingual glandular field, and exerts a defi- 

 nite influence on its development. 



As previously pointed out (Part III), this topographical relation of 

 the lingual nerve is a peculiar primate character, due to the brachio- 

 cephaly and the high development of the mandibular ramus obtaining 

 in the order. These primate characters are not shared by the more 

 generalized mammalian orders, and hence in them the Ungual 



