THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 69 



The primitive gland field of the alveoHngual gutter thus divided 

 by an obHque line falls into a craniolateral and a caudomesal tri- 

 angle, in which markedly different principles of development are at 

 work. In the lateral area small independent glands develop relatively 

 late in ontogeny, and no higher organization is attained than the tem- 

 porary association of the earlier sprouts with an epithelial keel. In the 

 mesal triangle the borders become the site of increased and cooperative 

 activity. At their caudal extremities relatively huge sprouts are 

 formed, the submaxillary and greater sublingual (cat). Anlages ap- 

 pear early, grow with great rapidity, and produce relatively enormous 

 secretory surfaces. In the cranial portion keels are formed which 

 supply the ducts, and only late, if at all, give rise to gland sprouts. 

 The ducts are, in the view outhned above, provided by the suppression 

 of individual glands, the price of organization. But it is noteworthy 

 that here, as in the vascular system, the direction of specialization 

 has been to manufacture a smaller number of highly efficient organs, 

 by the selection of few and the suppression of many similar elements. 



SUMMARY 



1. The buccal sulcus in man gives rise to two constant derivatives, 

 the orbital inclusion and the parotid. There is some evidence to show 

 that an intermediate element may at times be formed, the orbito- 

 parotid. 



2. The orbital inclusion is a column of epithelium derived from the 

 caudal portion of the sulcus by a process of folding and constriction, 

 and comes thereafter to lie in the mesenchyme on the ental surface of 

 the masseter and internal pterygoid muscles. Exceptionally it is con- 

 tinuous with the parotid at the border of the masseter (Chievitz). 



3. From the lingual sulcus and a flange derived from its compres- 

 sion arise the subma.xillary and the greater sublingual (Bartholinian) 

 glands, and a mesal element which may prove to be the apical gland 

 (Nuhn-Blandin). 



4. The lesser sublingual glands (Rivinian) are diffuse glands of the 

 alveolingual region, some of which are at their first appearance as- 

 sociated with the sulcus at the lateral margin of the plica sublingualis 



