PRIMATE ALVEOLINGUAL SALIVARY AREA 127 



Thus one of the simplest, and at the same time most complete, pat- 

 terns of mammahan intermandibular salivary development can be 

 schematically represented in Figs, sa and 56. 



In the genetic analysis of this type, (Fig. 5a) development occurs by 

 cleavage of the uniform field in sagittal hues into four parallel ce])halo- 

 caudal districts, a, b, c and d. In the lateral (a) and medial (d) districts 

 the single glandular anlages of the sagittal rows I, II and X retain their 

 primiti\e individual character and open by separate orifices along the 

 mesal and lateral ridges. In the intervening region the cephalic 

 components of the two sagittal rows VI and VIII unite to form two 

 parallel and separate ducts draining the two compound glands b and c. 

 In the pattern shown in Fig. 6 the number of distinct glands is re- 

 duced to two (Fig. 6b). Of these the lateral element, a, extending 

 along the alveolar border, is composed of a double sagittal row of sepa- 

 rate glands, each with its own orifice opening on the alveohngual 

 ridge. The rest of the potential oral field yields by selection a com- 

 plex gland, b, with a single main excretory duct along sagittal line 

 VIII (Fig. 6a) which opens by a single orifice. Coronal and oblique 

 lines of duct development extend the drainage area of the main canal 

 into adjacent glandular districts, chiefly laterad of its own course. 



This plan of development results in the formation of a main 

 caudal trilobed gland (b, b' , b", Fig. 6a), whose duct (VIII) further 

 cephalad receives two additional lateral canals draining the accessory 

 glands .Y and f. 



It will be noted that four of the individual anlages entering into the 

 formation of these accessory glands (B\ C^ £^ F'^) are in the sagittal 

 gland line VI, which in the precedhig pattern (Fig. 5a) served for the 

 development of the duct of the intermediate gland (b). Also that 

 the body of this latter gland (Fig. 5a) contains four components {I\ 

 P, K\ K-') which in Fig. 6(7 form the lateral element in the trilobed 

 main gland and drain along the oblique duct H'^G' into the princi- 

 pal duct fomied along line VIII. Individual adult types offer, 

 therefore, two conditions which must be considered in determining 

 homologies : 



I. Secretory glandular fields of identical derivation may drain 

 cephalad by separate parallel ducts along sagittal lines to separate ori- 

 fices, or they may empty by shorter coronal or oblique ducts into an ad- 



