278 EXCRETION. 



it is evident that the ideas of physiologists, with regard to 

 any excretory function of the liver, must have been very 

 indefinite before the relations of cholesterine had been de- 

 termined. 



The first question which arises is whether the liver has 

 any excretory function. Some authors, notably Blondlot, 

 have assumed that the bile is purely excrement! tious and 

 has no function as a secretion. This question we have fully 

 discussed in another place. 1 The confusion that has arisen 

 with regard to this point has been due to the fact that those 

 who adopted the view that the bile was simply an excretion 

 denied to it any digestive properties ; while, on the other 

 hand, those who believed it to be concerned in digestion 

 would not admit that it was an excretion. "We have shown 

 conclusively, in treating of intestinal digestion, that the bile 

 is so important in this process, as to be essential to life ; but 

 we have shown, at the same time, that the liver eliminates 

 from the blood one of the most important of the products of 

 disassimilation. It will be found important, as bearing upon 

 the probable function of the bile, to apply to this fluid the 

 general considerations contained in the first chapter, on the 

 distinctions between secretions and excretions. 



Cells of glandular epithelium are constantly manufac- 

 turing, out of materials furnished by the blood, the elements 

 of the true secretions ; but these elements do not preexist 

 in the blood, they appear de novo in the secreting organ, 

 and never accumulate in the system when the function of the 

 secreting organ is disturbed. Again, the true secretions are 

 not discharged from the body, but have a function to perform 

 in the economy, and are poured out by the glands intermit- 

 tently, at the times when this function is called into action. 

 As far as the biliary salts (the taurocholate and glycocholate 

 of soda) are concerned, the bile corresponds entirely to the 

 true secretions. These principles are manufactured by the 

 liver, they do not preexist in the blood, and they do not ac- 



1 See vol. ii., Digestion, p. 362, et seq. 



