SALIVARY GLANDS. 259 



By means of various -methods the existence of a network of 

 tubules surrounding the glandular cells may be demonstrated both 

 in the serous and mucous glands. The same arrangement may be 

 observed in the case of the cells forming the demilunes. The 

 course of these tubules may be followed to their junction with the 

 lumen of the secreting portion of the gland tubule, and the whole 

 structure would seem to indicate that the entire surface of the cells 

 is concerned in the act of secretion (Erik Muller, 05 ; Stohr 



^ TT\ ^ ^ 



96, II). 



As to the part that the intermediate tubules and the intralobular 

 tubes play in the process of secretion, Merkel's (83) theory is of 

 interest. He believes that the former yield a part of the water in 

 the saliva, while the salts are furnished by the rod-shaped epithe- 

 lium of the intralobular tubes. These views of Merkel have been 

 questioned, as it has been shown by chemic analysis that the 

 relative quantity of water and salts in the secretion of the salivary 

 glands is not at all proportionate to the number of the intermediate 

 tubules and intralobular tubes. For example, Werther finds that 

 although a great many intermediate tubules are present in the par- 

 otid gland of the rabbit and none at all in the submaxillary gland 

 of the dog, nevertheless the secretions of these glands contain equal 

 quantities of water. Furthermore, the secretions of the parotid of 

 the rabbit and of the sublingual of the dog show equal quantities of 

 salts, in spite of the fact that in the former there are large numbers 

 of intralobular tubes with rod-shaped epithelium and in the latter 

 none at all. 



THE SMALL GLANDS OF THE MOUTH. 



Besides the larger glands, there are in the oral cavity numerous 

 small lobular, tubulo-alveolar and simple branched tubulo-alveolar 

 glands. They are mostly glands with mucous secretion. In 

 many of them demilunes of Heidenhain may be made out, most 

 clearly in those of the lips (J. Nadler). They are known, accord- 

 ing to their location, as glandulae labiales, palatinae, and linguales. 

 The absence of intralobular tubes and well-defined intermediate 

 tubules is characteristic of all the smaller glands of the oral cavity. 

 As a consequence the secreting tubules are composed almost 

 entirely of those parts corresponding to the acini of the larger 

 glands. Branched tubular glands, with serous secretion, known 

 as v. Ebner's glands, occur in the tongue, their ducts opening into 

 the depressions of the circumvallate and foliate papillae, while the 

 secreting tubules extend into the muscular portion of the tongue. 

 The general character of v. Ebner's glands is shown in Fig. 204. 



The salivary glands and smaller glands of the mouth have a 

 rich blood supply. In the salivary glands the arteries follow the 

 ducts through their repeated branching, ultimately ending in capil- 

 laries which form a network inclosing the acini and the terminal 



