290 EXCRETION. 



is separated from the blood by the liver ; and here we may 

 note, in passing, a striking coincidence between the analysis 

 in a previous experiment, in which the blood was studied in 

 its passage through the brain, and the one just mentioned, 

 where the blood was studied in its passage through the liver. 

 The gain of the arterial blood in cholesterine in passing 

 through the brain was 23*307 per cent., and the loss of this 

 substance in passing through the liver is 23*309 per cent. 

 There must be, of course, the same quantity separated by 

 the liver that is produced by the nervous system, it being 

 formed, indeed, only to be separated by this organ, its for- 

 mation being continuous, and its removal necessarily the 

 same, in order to prevent its accumulation in the circulating 

 fluid. The almost exact coincidence between these two 

 quantities, in specimens taken from different animals, though 

 not at all necessary to prove the fact just mentioned, is still 

 very striking. 



It is shown by Experiment II. that the portal blood, as it 

 goes into the liver, contains but a small percentage of cho- 

 lesterine over the blood of the hepatic vein, while the per- 

 centage in the arterial blood is large. The arterial blood is 

 the mixed blood of the entire system ; and as it probably 

 passes through no organ before it gets to the liver, that di- 

 minishes its cholesterine, it contains a quantity of this sub- 

 stance, which must be removed. The portal blood, coming 

 from a limited part of the system, contains less cholesterine, 

 though it gives up a certain quantity. In the circulation of 

 the liver, the portal system largely predominates, and is 

 necessary to other important functions of this organ, such 

 as the production of sugar ; but soon after the portal vein 

 enters the liver, its blood becomes mixed with that from 

 the hepatic artery, and from this mixture the cholesterine is 

 separated. It is only necessary that blood, containing a 

 certain quantity of cholesterine, should come in contact with 

 the bile-secreting cells, in order that this substance be sepa- 

 rated. The fact that it is eliminated by the liver is proven 



