1 82 ELEMENTS OF HISTOLOGY, [chap. xxn. 



neck is the only portion of the intermediary part 

 present, 'e.g., in the sub-maxillary and orbital glands 

 of dog and cat, and in the sub-lingual of the rabbit. 

 In others, especially in the serous salivary glands, as 

 in the parotid of man and mammals, sub-maxillary of 

 rabbit and guinea-pig, and in the mixed salivary 

 e.g., sub-maxillary and sub-lingual of man and ape 

 there exists after the neck a long intermediary part, 

 which gives off several shorter or longer branches of 

 the same kind, all of which terminate in alveoli. 



243. The alveoli or acini are the essential 

 or secreting part of the gland ; they are flask-shaped, 

 club-shaped, shorter or longer cylindrical tubes, more 

 or less wavy, or if long, more or less convoluted; 

 many of them are branched. Generally several open 

 into the same intermediary part of a salivary tube. 

 The alveoli are much larger in diameter than the 

 intermediary part, and slightly larger, or about as 

 large, as the intralobular ducts. But there is a 

 difference in this respect between the alveoli of a 

 serous and a mucous salivary gland ; in the former 

 the alveoli are smaller than in the latter. 



The membrana propria of the intermediary duct 

 is continued as the membrana propria of the alveoli. 

 This is a reticulated structure, being in reality a basket- 

 shaped network of hyaline branched nucleated cells 

 (Boll). The lumen of the alveoli is very minute in 

 the serous, but is considerably larger in the mucous 

 glands ; it is in both glands smaller during secretion 

 than during rest. 



244. The epithelial cells lining the alveoli are 

 called the salivary cells they are of different 

 characters in the different salivary glands, and chiefly 

 determine the nature of the gland. The cells are 

 separated from one another by a fluid albuminous 

 cement substance. (1) In the serous or true salivary 

 glands, as parotid of man and mammals, sub-maxillary 



