NITKOGENIZED ALIMENTARY PRINCIPLES. 49 



rendering it slightly viscid, but on cooling, the whole mass 

 becomes of a more or less gelatinous consistence, according 

 to the quantity of gelatine that is present. A considerable 

 quantity of inorganic matter, particularly phosphate of lime, 

 is always present in combination with gelatine. 



Gelatine and chondrine present slight differences as re- 

 gards their chemical reactions, in other respects being nearly 

 identical. The sulphate of alumina, alum, and the sulphate 

 of iron, will precipitate chondrine, but have no influence on 

 a solution of gelatine. Tannin, or infusion of galls, added 

 to a solution of gelatine, produces a brownish precipitate. 

 This reaction is marked in a solution containing but one 

 part of gelatine to five thousand of water. Both gelatine 

 and chondrine are of indefinite chemical composition and 

 uncrystallizable. 1 By the action of sulphuric acid, gelatine 

 is transformed into a crystallizable substance called glyco- 

 colle, which has a sweetish taste, is soluble in water and 

 insoluble in alcohol and ether. According to some, this is 

 capable of being separated into alcohol and carbonic acid 

 by fermentation. 2 



A great deal of interest was at one time attached to gela- 

 tine as an article of food, from the fact that it is formed and 

 extracted from parts, particularly the bones, which were 

 before regarded as comparatively useless. Indeed, the ex- 

 periment of diminishing the quantity of meat, and supplying 

 in its place the extract of bones, was made in several hospi- 

 tals and manufacturing establishments in France ; but this 

 change in diet led so universally to complaints of insufficien- 

 cy of food, that experiments were soon instituted with a view 

 of determining whether gelatine really possessed any nutritive 

 power. "Without entering upon a full discussion of these exper- 



1 The formulae generally given for these two substances are: Gelatine, C 18 

 H^OsN^j, and Chondrine, C 32 H 26 Oi 4 N 4 ; but, as remarked by Longet, these 

 formulae are very uncertain. Chondrine is supposed by some (Mulder, Robin) to 

 contain, in addition, a little sulphur. 



2 LONGET, Traite de Physiologic, Paris, 1861, tome i., p. 44, note. 



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