8 THE ANATOMY OF THE ADULT HUMAN SALIVARY GLANDS 



to further growth and topographical changes in the mandible, pro- 

 ducing an angular transition between ramus and body of the lower 

 jaw, with coincident elongation of the earlier premasseteric segment 

 of Stenson's duct (Fig. i), while, on the other hand, reduction of the 

 earlier continuous periductular efSorescence may also help to clear 

 the masseteric segment of the duct and define more sharply its relation 

 to the retromasseteric parotid gland proper. This view would rea- 

 sonably account for the adult retention of the accessory parotid glands 

 {socicE parotidis) on the basis of unusual persistence and further devel- 

 opment of certain of the earlier periductular glandular sprouts. 



Thus no better illustration of the persistence of earlier develop- 

 mental conditions could be afforded than by the comparison of Figs, i 

 and 3. In the latter adult individual the secondary or associate 

 parotid elements, indicated in Fig. i by the periductular efflores- 

 cence, have developed into distinct glandular masses {6) emptying into 

 both dorsal and ventral borders of Stenson's duct (5) and surrounding 

 the same nearly to the cephahc margin of the masseter. In this case 

 practically all of the glandular elements surrounding the masseteric 

 segment of the parotid duct in the earlier fetal stage (Fig. i) have 

 been carried over into the adult organization. 



The same iype of profuse parotid development along the course 

 of the masseteric segment of the duct is characteristic, among the 

 lower primates, chiefly in certain genera of the group of the Old World 

 Cercopithecidffi. Thus Fig. 4 shows the parotid complex of one of 

 the Cynocephalidae (Cyiioccphalus porcarius) in which the hammer- 

 shaped parotid glandular prolongation accompanies and nearly 

 envelops Stenson's duct up to the point of its engagement in the buc- 

 cinator. 



In contradistinction, a specimen of Macacus rhesus (Fig. 5), from 

 the Morphological Museum of Princeton University (No. go6), 

 shows the opposite type of general parotid development in primates, 

 in which the entire parotid gland proper has receded into a retro- 

 masseteric position, surrounding the caudal margin of the external 

 auditory meatus and extending thence into submandibular and 

 sternomastoid regions. On the other hand, in the adult human 

 individual instance shown in Fig. 6, the ventral circumference of the 

 parotid duct is free, while its dorsal border is incrusted by a fully 



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