280 EXCRETION. 



bile contained in this organ the crystalline lens, and the 

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

 nervous system and blood. Two views present themselves 

 with regard to its origin. It is either deposited in the- ner- 

 vous matter from the blood, or is formed in the brain and 

 taken up by the blood. This is a question, however, which 

 can be settled experimentally, by analyzing the blood for 

 cholesterine as it goes to to the brain by the carotid, and as 

 it comes from the brain by the internal jugular. The cho- 

 lesterine being found also in the nerves, and, of course, a 

 large quantity of nervous matter existing in the extremities, 

 it is desirable at, the same time to make an analysis of the 

 venous blood from the general system. 



With a view of determining this question, we made the 

 following experiments : 



Experiment I. In this experiment, specimens of blood 

 were taken from the carotid, the internal jugular, the vena 

 cava, hepatic veins, hepatic artery, and portal vein, in a liv- 

 ing animal (a dog about six months old). In addition, we 

 took a specimen of bile from the gall-bladder, and some of 

 the substance of the brain. These were all carefully ex- 

 amined for cholesterine, and the following were the main 

 results : In the brain cholesterine was found in large quan- 

 tity. There was no cholesterine in the extract of the blood 

 from the carotid, examined three days after, and but a few 

 crystals, eleven days after. Cholesterine was almost imme- 

 diately discovered in the extract of the blood from the in- 

 ternal jugular, and the crystals were present in large num- 

 bers on the twelfth day. In this experiment the animal was 

 etherized when the blood was taken, and the examinations 



1 In 1854, Marcet described a substance extracted from the spleen, which 

 he thought was analogous to cholesterine (An account of the Organic Chemical 

 Constituents, or Immediate Principles of the Excrements of Man and Animals 

 in the Healthy State. Philosophical Transactions, London, 1854, p. 269); and in 

 1857, he fully recognized its existence in this organ (On the Immediate Prin- 

 ciples of the Excrements of Man and Animals in the Healthy State. Philosophical 

 Transactions, London, 1857, p. 412). 



