456 EXCRETION. 



ation was so prolonged, that it was not thought worth while to complete the analysis, 

 and the experiment was abandoned. In the following experiment we were more suc- 

 cessful. 



Experiment II. A good-sized bitch (pregnant) was brought completely under the 

 influence of ether, the abdomen was laid freely open, and blood was drawn, first from the 

 hepatic vein, and next from the portal vein. The taking of the blood was entirely satis- 

 factory, the operation being done rapidly, and the blood collected without any admixture. 

 A specimen of blood was then taken from the carotid, to represent the blood from the 

 hepatic artery, assuming that the arterial blood is of uniform composition. 



The three specimens of blood were then examined in the usual way for cholesterine, 

 with the following results 



Quantity of blood. Cholesterine. Cholesterine per 



grains. grains. 1,000 pts. 



Arterial blood 159-537 0'200 1'257 



Portal vein 168'257 0'170 1'009 



Hepatic vein 79-848 0'077 O964 



Percentage of loss in arterial blood in its passage through the liver 23-309 



Percentage of loss in the blood of the portal vein 4-460 



This experiment proves positively, what there was good ground for supposing from 

 Experiment I., that cholesterine 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 men- 

 tioned, where the blood was examined after 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 as is produced by the nervous 

 system, it being formed, indeed, only to be separated by this organ, its formation 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 cholesterine 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 which diminishes its cholesterine 

 before it gets to the liver, it contains a quantity of this substance which must be removed. 

 The portal blood, coming from a limited part of the system, contains less cholesterine, 

 although it gives up a certain quantity. In the circulation in 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 sep- 

 arated. 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 shall be 

 separated. The fact that it is eliminated by the liver is proven with much less difficulty 

 than that it is formed in the nervous system. In fact, its presence in the bile, and the 

 necessity of its constant removal from the blood, consequent on its constant formation 

 and absorption by this fluid, are almost sufficient in themselves to warrant the conclusion 

 that it is eliminated by the liver. This, however, is put beyond a doubt by the preceding 

 analyses of the blood going to and coming from this organ. 



In treating of the composition of the fa3ces, we have considered so fully the changes 

 which the cholesterine of the bile undergoes in its passage down the intestinal canal, that 

 it is not necessary to refer to this portion of the subject again. We have made but one 

 examination of the quantity of stercorine contained in the daily fecal evacuation, and, 



