130 PRIMATE ALVEOLINGUAL SALIVARY AREA 



development of the primitive anlages forming the genetic lines / and 

 // (Fig. 7a). 



2. An intermediate gland (b) whose separate duct develops by con- 

 crescence of the sagittal anlages of line VI cephalad of the coronal 

 level H, beliind which point the secreting epithelium of the gland proper 

 arises from anlages !■', P, P. The duct of the gland receives at level 

 D a lateral duct draining a small accessory gland (a) formed by 

 anlages £>', D\ E' and E\ 



3. A mesal gland (c) formed in its chief part by anlages P, K^, K'^ 

 and A'^, and draining by a duct developed cephalad along line VIII. 

 At coronal level F tliis duct receives the outlet of a small accessory 

 gland (F) formed by anlages G\ W, W°. 



4. Along the mesal border of the field a broken series of single 

 separate glands containing two cephahc ((f) and three caudal (d') 

 components. These represent the partial development of some of the 

 anlages of sagittal hne X. 



Figs. 8a and 8b show respectively the genetic ground plan and the 

 resulting adult t>'pe of a fonn in which, compared with the preceding 

 Figs. 7a and 76, without altering the total number of the component 

 anlages involved, a different result is obtained. Only a single major 

 duct (c) exists, which, shortly prior to its termination, is joined laterally 

 by the duct of gland b. This, from the gross anatomical standpoint, 

 important difference in the organization of the cliief intermandibular 

 glands and their ducts, may be assumed to have occurred by the single 

 exchange of a coronal for a sagittal anlage, as shown in the schemata 

 ya and Sa. li VI A^ of the former pattern had not developed into 

 the terminal of the independent duct b, but if in its place VII B' had 

 been emplo\'ed as a coronal link between the conducting lines VI 

 and VIII, then the conditions shown in Figs. 8a and &b would 

 have resulted. 



The two conditions just discussed find their concrete illustration in 

 the two relations exhibited in the adult human subject between the 

 ducts of the submaxillary and greater sublingual (Bartholinian) glands 

 when the latter structure develops as one of the major glands of the 

 intermandibular complex. 



It is thus not dififtcult to see how by slight shifting in the selection 

 of the available genetic anlages and a small increase in the number of 



