36 THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 



of a pyriform shape, slightly flattened on its ental surface, and has 

 a rather broad pedicle connecting it with the oral epitheHum. The 

 enlarged dependent fundus bulges forward as well as backward of its 

 pedicle, coming thus to exceed it considerably in sagittal extent. In 

 the sections (Figs. 12-14) passing through the pedicle, it is seen that 

 the attachment is sulcal, and that the pedicle, projecting nearly 

 horizontally laterad, makes an approximately right angle with the 

 ventrolateral^ directed fundus. The latter is a solid mass of cells, 

 staining rather faintly at its center, where, however, the nuclei are 

 perfectly distinguishable and no trace of a cleft or lumen is seen. 

 Evidently at this stage of development there is no question of an 

 open duct. 



The sections immediately craniad of the pedicle require a rather 

 minute consideration, for upon such e\-idence as they afford must 

 be based our opinion of the mode of formation of the pro.ximal portion 

 of the parotid duct. This question necessarily involves the further 

 question of the displacement of the parotid orifice secondarily from its 

 point of origin, by the formation of a duct or duct segment anterior 

 in position to the primitive anlage. To anticipate, it may here be 

 stated that subsequently, for a time, the parotid has a point of attach- 

 ment nearer the angulus oris than in this embrj'o. A secondary dis- 

 placement must therefore be accepted as occurring. As this displace- 

 ment is absolute and not relative, it must be inferred that it is due to 

 an actual carr)ing forward of the pedicle along the buccal sulcus. 

 Two possibilities offer : the advance of the duct may be due either to 

 the proliferation of a crest or to the formation of a fold, which in 

 turn might, or might not, have a lumen. In either case a process of 

 constriction must supervene to free the duct from the oral epitheUum. 



On the right side of this embryo of 20 milhmeters the five sections 

 immediately in front of the parotid pedicle are represented in Figs. 8-12. 

 The first of these shows the buccal sulcus without indication of any 

 process of duct formation. The ventral convexity is here very shght, 

 and the inferior alveobuccal sulcus is ill-defined. The next four show 

 a flange projecting from the buccal sulcus and increasing in breadth as 

 the parotid is approached. In the last the flange has attained an 

 extent corresponding to the horizontal portion and angle of the pedicle 

 in the next section (Fig. 12). In its first sections (Figs, q and 10) it 



