30 The Anatomy of the Salivary Glands 



were invariably found in the duct cells of different glands and 

 species, but the acinar reaction was very variable in different glands 

 but nearly always much weaker than in the ducts (Burstone, 1956; 

 Hill and Bourne, 1954; Noback and Montagna, 1947). Lipase was 

 found by Martin (1953) in the interlobular ducts of the dog sub- 

 maxillary glands. The acini were negative as were all cells in the 

 parotid. The serous acini of the guinea pig submaxillary gland 

 were positive. Hill and Bourne (1954) did not find positive reac- 

 tions in the cat, guinea pig, mouse or rat. 



Amino peptidase has been demonstrated in the interlobular 

 ducts of the human parotid and submaxillary glands (Burstone and 

 Folk, 1956). 



Dehydrogenases. High concentrations of succinic dehydrogenase 

 have been found in the duct cells of the rat, guinea pig and rabbit 

 with much less enzyme in the acinar cells (Padykula, 1952; Stier, 

 1952; Neumann, 1952; Hill and Bourne, 1954). It is interesting 

 that Stier also found a high concentration of this enzyme in the 

 pancreatic ducts. 



EMBRYOLOGY AND MATURATION 



The salivary glands develop as groove-like outgrowths of the 

 oral epithelium which subsequently becomes a solid rod of epithe- 

 lium budding to form lobules. The rod develops a lumen and 

 becomes a tube as a result of degeneration of the most centrally 

 placed cells (Chievitz, 1885; Schulte, 1913; Borghese, 1950). The 

 ducts at this stage are lined by a multi-layered epithelium similar 

 to that found in the adult main ducts. The general form of the 

 glands is established at this stage although the epithelium is still 

 relatively undifferentiated. In man the parotid anlage appears at 

 8-12 mm, the submaxillary at 12-14 mm and the sublingual at 

 20-24 mm > tne parotid and submaxillary ducts begin to ramify 

 after 20 mm is reached (Bujard, 191 1). The acini are later develop- 

 ments which bud off the terminal tubules to give first of all simple 

 alveoli which then may become differentiated into serous and 

 mucous cells and finally to demilunes (in those glands possessing 

 them). In man it appears that primitive acini are already formed in 

 the 138 mm (4th month) foetus and presumably are mature at birth 

 (de Plessis, 1957); in the cat on the other hand the submaxillary 

 gland is incompletely differentiated at birth and reaches maturity 

 a few weeks after birth (Takagi, 1925). In the rat no acini are 



