HYDROCARBONACEOUS SUBSTANCES. 



71 



fact that it is often taken with the food in noticeable quantity and 

 consumed in the body, without any increase of the internal adipose 

 deposit. In cases of acute wasting disease, of temporary abstinence, 

 and in the hibernation of animals, the fat previously stored up greatly 

 diminishes or disappears altogether. In these instances the oleaginous 

 matter which disappears from the body is not to be found in the excre- 

 tions. The sebaceous secretion of the skin is the only form of fatty 

 matter discharged externally, and this is far inferior in quantity to 

 that taken with the food and consumed by the system. The fat which 

 thus disappears is therefore disposed of by decomposition in the body. 

 We cannot follow with any certainty the steps of this decomposition, 

 nor determine the successive alterations which take place in the fatty 

 substance during its passage through the system. But it undergoes 

 changes of some kind by which its essential characters are lost, and 

 its elements are finally discharged under another form in the products 

 of excretion. 



Cholesterine, C 26 H 4 ,0, 



So called from its occurring as a solid deposit from the bile, in which 

 form it was first discovered. It is included in the present group of 

 organic compounds, owing to its being crystallizable and non-nitroge- 

 nous. But it has no real affinity with the fatty matters, although it 

 resembles them in certain physical properties, such as its insolubility 

 in water, and its solubility in ether, boiling alcohol, chloroform, oily 

 liquids, and solutions of the biliary salts. It is incapable of saponifi- 

 cation, and at a high temperature (360 C.) may be volatilized without 

 decomposition. Its solutions rotate the plane of polarization to the left 

 32. It is deposited from its 



alcoholic or ethereal solution in FIG. 10. 



the form of thin, colorless, trans- 

 parent, rhomboidal plates, por- 

 tions of which are often cut out 

 by lines of cleavage parallel to 

 the edges of the crystal. They 

 frequently occur deposited in 

 layers, in which the outlines of 

 the subjacent crystals show very 

 distinctly through the substance 

 of those above. If the crystals 

 be treated with a mixture of 1 

 volume of water and 5 volumes 

 of sulphuric acid, and gently 

 warmed, their borders take a 

 bright carmine color, changing 

 afterward to violet . (Gorup- 

 Besanez.) 



If triturated with strong sulphuric acid, they yield, on the addition 

 of chloroform, a blood-red color, which afterward disappears by expo- 



CHOLESTERINE, from the contents of an encysted 



tumor. 



