ORIGIN OF CHOLESTERIN . 369 



traces exist in the bile. The excretory action of the liver will be con- 

 sidered, in this connection, with reference to the bile itself. At the 

 present day it is admitted that the bile is an excretion as well as a 

 secretion ; and this question has been 'fully discussed in connection 

 with the physiology of digestion. The constant and invariable pres- 

 ence of cholesterin in the bile assimilates it in every regard to the 

 excretions, of which the urine may be taken as the type. Cholesterin 

 always exists in the blood and in certain of the tissues of the body. It 

 is not produced in the substance of the liver, but is merely separated 

 from the blood by this organ. It is constantly passed into the intestine, 

 and is discharged, although in a modified form, in the feces. Physiolo- 

 gists know of no office which it has to perform in the economy, any 

 more than urea or any other of the excrementitious constituents of the 

 urine. It accumulates in the blood in certain cases of organic disease 

 of the liver and gives rise to grave nervous symptoms. 



Origin of Cholesterin. Cholesterin exists in largest quantity in the 

 substance of the brain and nerves. It is also found in the substance of 

 the liver probably in the bile contained in this organ the crystalline 

 lens and the spleen ; but with these exceptions, it is found only in the 

 nervous tissue and blood. It is either deposited in the nervous matter 

 from the blood or it is formed in the brain and taken up by the blood. 

 This is a question, however, that can be settled experimentally. 



In a series of experiments made in 1862, it was invariably found that 

 the proportion of cholesterin in the blood of the internal jugular vein 

 and the femoral vein was greater than in the arterial blood. In experi- 

 ments made on dogs not etherized, the blood of the jugular vein con- 

 tained, in one instance 23.3 and in another 59.8 per cent more choles- 

 terin than the arterial blood of the same animals. The blood of the 

 femoral vein contained about 6.3 per cent more cholesterin than arterial 

 blood. In three cases of hemiplegia, cholesterin was found in normal 

 quantity in blood taken from the arm of the sound side, while blood 

 from the paralyzed side contained no cholesterin (Flint). 



These observations point to the production of cholesterin in the 

 tissues ; and the fact of its existence, under normal conditions, in the 

 nervous tissue renders it probable that the chief seat of its formation is 

 the substance of the nerve-centres and nerves. The question of its 

 production in the spleen is one that has not been investigated. 



In another series of experiments, it was shown that the blood lost 

 cholesterin in passing through the liver. In one observation it was 

 found that the arterial blood lost a little more than 23 per cent and the 

 portal blood about 4^ per cent, in passing through the liver (Flint). 



The portal blood, as it goes to the liver, contains but a small per- 



2B 



