30 



PHYSIOLOGY OP FARM ANIMALS 



[CH. 



maxillary glands, which lie in the lower jaw on each side. Their 

 ducts open at the side of the root of the tongue. (3) The sub- 

 lingual glands, placed underneath the tongue in the floor of the 

 mouth, with several ducts opening close together. 



The salivary glands are developed in the embryo in the form 

 of buds which spring from the epithelium lining the inside of the 

 mouth. These buds are at first solid but gradually become 

 hollowed out and undergo a process of ramification so as to form 

 lobules which when fully developed are bound together with 

 connective tissue. In their mode of origin and also structurally 

 they may be regarded as typical of secreting glands generally. 



Histologically there are two kinds of salivary glands, mucous 

 glands and serous glands. The parotid glands are generally 



^Duci 



Mucous 

 Cells V/ -\ ' 



V.^^ 





^^ Nodule of 

 Serous Cells 



Fig. 20 





Submaxillary salivary gland of dog. 



composed of purely serous cells, whereas the submaxillary and 

 sublingual glands are mixed glands, containing both mucous and 

 serous constituents. 



Each lobule of a salivary gland is composed of saccular or 

 tubular alveoli or acini from each of which a duct passes, uniting 

 with similar ducts from other alveoli to form the main duct of 

 the gland. The alveoli are enclosed by a basement membrane 

 within which are the glandular epithelial cells. In the case of 



