82 ORGANIC CONSTITUENTS. 



are known as suet. Stearin is the principal constituent of suet ; 

 margarin of fat or lard. Human fat affords a good illustration 

 of the proper fats. It solidifies at 62° ; but the consistence is 

 not constant even in the same person — for instance, the fat of 

 the kidneys is perfectly solid at 62°, while the fat of the sub- 

 cutaneous tissue remains fluid as low as 59°. 



The non-sciponifiable fats. 



a. Cholesterin is a normal constituent of the bile, of the 

 brain, and of the spinal cord. It has been found by Lecanu, 

 Denis, Boudet, jNIarchand, and Simon, in the blood ; by 

 Fromherz and Guggert in the vei'nix caseosa ; by Breschet, 

 Wohler, and Marchand in hydrocele : by Stromeyer in an 

 encysted tumour in the abdomen of a woman : by Breschet 

 and Barruel in the ovary and testicle in a diseased state ; by 

 Caventou in an abscess of the tooth; by Lassaigne in a scirrhous 

 structure in the mesocolon ; by Guggert in fungus medullaris ; 

 by Marchand in medullaiy sarcoma; and by Drunty in a vesical 

 calculus extracted from a dog. It sometimes exists in a state 

 of solution, while in other cases it floats on the surface, either 

 in the fonn of brilliant scales, or of solid masses. It has 

 never been found in any of the plants which are used for food; 

 but Dumas has found a substance of a similar composition in 

 the resin of the pine. 



In order to obtain it from biliaiy calculi, we must first treat 

 these with boiling water, then triturate, dry and pulverize the 

 residue, treat it with boiling alcohol, filter it while still hot, and 

 allow it to cool very gradually. The cholesterin separates itself 

 in the form of white, sparkling, transparent scales. These 

 should be collected in a filter, again dissolved in hot alcohol, 

 and allowed to recrystallize. In this state it will be tolerably 

 pure, Berzelius recommends the prenous addition of a few 

 drops of caustic potash or ammonia, in order to saponify any 

 stearic or margaric acid that may be present. 



In order to obtain it from the brain, that organ must first 

 be deprived of all its water, by being finely triturated and then 

 placed upon the water-bath. This being fully accomplished it 

 must be treated with ether, and afterwards with boiling alcohol, 

 until these fluids cease to abstract anything more. As the 

 alcoholic solution cools, a white powder is precipitated. By 



