CHEMICAL BASIS OF THE ANIMAL BODY. 1241 



gon is decomposed, yielding the several products which result 

 from the decomposition of lecithin under the same conditions, 

 together with an additional product known as cerebrin. 



Cerebrin. 



Is obtained as a product of the decomposition of protagon 

 when brain-substance is boiled with baryta-water and then 

 extracted with hot alcohol. It separates out from this latter 

 solvent when cooled at 0°, and may be purified by recrystalliza- 

 tion. 



It is a light, colourless, slightly hygroscopic powder, which 

 swells up in water. When heated to 80° it turns brown, and 

 • at a higher temperature (160°) melts, bubbles up and finally 

 burns away. It is insoluble in cold alcohol or ether ; warm 

 alcohol dissolves it readily. It appears probable that at least 

 three closely allied substances may be present in the product 

 as above described, a fact which points to the possible existence 

 of several forms of protagon. The cerebrins, when boiled with 

 dilute sulphuric acid, yield a sugar which has recently been 

 shewn to be identical with galactose. (See above, p. 1220.) 



Charcot's Crystals. 



These remarkable crystals, whose chemical nature and 

 significance have been the subject of much surmise, were first 



Fig. 200. Charcot's Crystals. (Krukenberg.) 



described by Charcot in the spleen and blood of leukhsemic 

 patients. Later researches have confirmed their characteristic 

 appearance in this disease and have further shewn that they 

 occur in health, more particularly in semen, but also in various 

 tissues ; they are also found in asthmatic expectorations. They 

 may be readily obtained from semen by extracting, with warm 

 water to which a little ammonia has been added, the residue 

 which remains after semen has been treated with boiling 



