CERVUS ELAPHUS. 



CHEMICAL AND MEDICAL PROPERTIES AND USES. 



Pure hartshorn shavings, which are formed by planing down 

 the internal white part of the horn, yield to water, by de- 

 coction, 27 parts of gelatine, -4- 57.5 of phosphate of lime, 

 -f- 1.0 of carbonate of lime, + 14.5 of water, = 100.0 of the 

 horn. The gelatine is inodorous and insipid, and has all the 

 chemical properties of pure gelatine. 



The retention of hartshorn in the list of the Materia Medica 

 is the relic of a period of inert practice : it yields a light and 

 sufficiently nutritious article of diet for the sick and the 

 convalescent, but this very quality renders it useless as a 

 medicine. 



Gelatine, when freed from water by evaporation, so as to 

 become brittle, is not susceptible of change, and may be kept 

 for any length of time. For medicinal use it should there- 

 fore always be kept in the dry state. But when it is united 

 with so much water as to render it tremulous, it soon under- 

 goes decomposition, first becoming acid, then exhaling a 

 foetid odor, and putrefaction takes place. Exposure to the 

 air is not necessary to effect this change in gelatine. When 

 exposed to a high temperature it first whitens, then shrivels, 

 and is carbonized : tremulous gelatine melts before it under- 

 goes these changes. When tincture of galls or any astrin- 

 gent vegetable solution is dropped into a solution of gelatine, 

 an insoluble precipitate takes place. This is tawwo-gelatine, a 

 compound of the gelatine and tannic acid, and it is this com- 

 bination that produces leather. Gelatine, like gum, renders oils 

 miscible with water, forming emulsions. Alcohol and ether 

 do not dissolve gelatine, but they separate it from the water of 

 its solution ; in a thin solution, however, neither alcohol nor 

 ether produces any obvious change. All the concentrated 

 acids decompose gelatine, but diluted acids dissolve it un- 

 changed. When chlorine gas is mixed with a solution of 

 gelatine, a white solid matter, in filaments, is separated, which 

 Bouillon la Grange has named oxygenized gelatine, but the 

 nature of this change is unknown. The alkalies assisted by 

 heat dissolve gelatine, but do not produce soaps. None of the 

 earthy salts, with the exception of those of baryta, precipi- 

 tate its solution ; phosphate of soda, however, causes a slight 

 milkiness in it. Among the metallic salts, nitrate of silver 

 only precipitates the solution of pure gelatine. 



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