180 



ANATOMY AND PHYSIOLOGY. 



secrete (separate) bile : the salivary glands, we have seen, secrete 

 saliva ; and so on with others. It would be a mistake, however, 

 to suppose that secretion is performed only by glands, for thin mem- 

 branes, without any glandular structure, produce numerous secre- 

 tions ; and the deposition of the solid parts of the body takes place 

 without the intervention of anything like glands. It seems to be 

 the capillary vessels, themselves, in these cases, that are employed ; 

 and even in glands, however minutely we examine their structure, 

 there can be detected almost nothing but endless subdivisions of 

 circulating vessels, and ducts for collecting and carrying off the 

 secreted fluid. 



Intimate structure of a Composite Gland [the Parotid]. 



Representation of a Kidney 



The liver is the largest gland in the body. We have seen that 

 it secretes . the bile, which probably serves important purposes in 

 digestion. The numerous ducts of the liver unite and form one 

 large duct, called the hepatic duct, from which the bile passes into 

 the common duct, or into the gall-bladder, to be poured, when re- 

 quired- into the upper part of the intestinal canal. The bile is an 



