CHEMICAL PHYSIOLOGY, 



AND 



ITS POINTS OF CONTACT WITH PATHOLOGY. 



THE food of man, variously prepared by mechanical Digestion. 

 processes and chemical operations (cooking), is com- 

 minuted in the mouth by chewing. At the same 

 time it is mixed with a variety of fluids, some of 

 which have chemical powers and predispose the food 

 to a change, while others serve mechanical objects 

 only. The mixture of these fluids is termed saliva ; saliva. 

 but however homogeneous may appear that mixture, 

 the properties of its components are very various. 

 For the secretion of every particular kind of glands, 

 of which there are four, differs , and the secretion 

 of one and the same gland or set of glands may vary 

 according to the agencies which call them into action. 

 Underneath the forepart of the tongue is secreted from 

 one and the same duct the saliva of a gland which 

 lies under the tongue (sublingual) , and that of two 

 other glands which lie farther back on both sides of 

 the tongue underneath the lower jaw (submaxillary 

 glands). To collect either of these secretions little 



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