THE de\t:lopment of the salivary glands in man 39 



It has the outline of the handle and one ball of a dumb-bell. The 

 ball represents the parotid duct, the handle an intermediate region 

 which must be reduced to free the duct. The intermediate element 

 has convex borders, and is set off against both buccal sulcus and 

 parotid duct by slight constrictions. Were these conceived as broken 

 through, a mass of cells corresponding to the handle of the dumb-bell 

 would be interposed between the duct and the oral epithelium, resem- 

 bling in general the condition found on the right side of the 20 millimeter 

 embryo. In the cat such sections as this occur only in the presence 

 of an orbitoparotid. The appearances in this and the preceding 

 embryo suggest that a search for this element in man with more 

 abundant material might not be without results. 



9. Hammar. Embryo of 18.5 millimeters. The presence of con- 

 nective tissue is noted between the duct and the buccal sulcus. 



10. Columbia Collection, No. 3, length 22 millimeters. Obtained 

 by Professor J. A. Blake. The epidermis and oral epithelium have 

 in some places separated from the basement membrane ; the stain- 

 ing property of the tissue is somewhat impaired ; the paUium is in 

 folds, but the oral cavity and adjacent structures are fairly preserved. 

 The right side of the embryo was cut into sagittal sections, not however 

 quite to the median hne. The remainder was sectioned in the frontal 

 plane. The transverse sections are almost perfectly oriented, 30 fi in 

 thickness. The parotid on the left side springs from the buccal sulcus 

 240 M from the angulus oris. Its attachment which is parietal, being 

 displaced dorsad of the fundus of the sulcus, has a sagittal extent 

 of 60 /li. Its duct lies in the submasseteric position, the enlarged but 

 unbranched fundus resting against the side of the masseter near its 

 lower border, in a slight thickening of the mesenchyme. Owing to 

 poor preservation, no histological details can be observed. The or- 

 bital inclusion lies nearer the pterygoids than to the oral cavity. Its 

 length is 240 m; its anterior extremity, slightly enlarged, lies 300 /^ 

 behind the attachment of the parotid. On the right side, which was 

 cut sagittally, the parotid and the orbital inclusion present the same 

 general characters. 



11. Hammar. Embryo of 24.4 milHmeters length. The duct 

 opens into the buccal sulcus at an acute angle. The fundus is scantily 

 branched. 



