GELATINOUS COMPOUNDS. 67 



Fibrous tissue wherever it occurs, and by the animal basis of Bone, which is 

 nearly identical with this. It gelatinizes so strongly, that 1 part of it in 

 100 of water forms a consistent jelly on cooling. Its reaction with tannic 

 acid is so distinct, that the white cheesy precipitate which this reagent forms, is 

 visible in a solution of 1 part of glutin in 5000 of water. This, however, is 

 the only acid which throws down glutin from its aqueous solution ; and alkalies 

 have no other effect than that of precipitating a little bone-earth. Creosote 

 gives the solution a milky turbidity; but the only earthy and metallic salts 

 which precipitate it are corrosive sublimate, bichloride of platinum, and sul- 

 phate of binoxide of platinum. In this respect, as we shall presently see, glutin 

 differs markedly from chondrin. If the solution of glutin in hot water be 

 boiled for some time, it loses the property of gelatinizing, and at the same time 

 phosphate of lime is separated from it (Liebig's "Familiar Letters/ 7 p. 387, 

 note) ; and a similar effect is produced by repeatedly dissolving glutin in hot 

 water with exposure to air. Putrefaction takes place more readily in glutin 

 than in fibrin under similar circumstances; and according to Gannal, the 

 gelatigenous tissues are the first of the solid animal structures to become 

 putrid. Glutin does not seem to include phosphorus as one of its necessary 

 components; and the quantity of sulphur which it contains (about 0.50 per 

 cent., according to Prof. Liebig) is much smaller than that which enters into 

 the composition of the Albuminous substances. But it appears to form definite 

 chemical combinations with phosphate and carbonate of lime, since in the sub- 

 stance not merely of normal osseous tissue, but of the abnormal ossifications of 

 fibrous membranes, &c. no such Jicterogeneousness is seen, as would be produced 

 by a mere interstitial admixture of the organic and earthy matters. The latter 

 are easily separated, however, by the action of dilute acids. When Glutin is 

 boiled for some time in caustic potash, it is decomposed, with escape of ammonia; 

 and two new compounds, leucine and glycine are produced. The formation of 

 the first of these is of peculiar interest; since, as the same substance is obtain- 

 able by the same agency from the protein-compounds ( 19), a certain similarity 

 in the arrangement of the ultimate elements of these two bodies is indicated, 

 notwithstanding their differences in composition and characters. Glycine (or 

 gelatin-sugar) is an organic base of much interest in its relations to certain 

 excretory substances, as the hippuric acid of the urine, and the glycocholic acid 

 of the bile ( 58, 68) ; it has a strong sweet taste, and is very soluble in water, 

 from which it may be crystallized like ordinary sugar; and its composition is 

 comparatively simple, its formula being 4 Carbon, 4 Hydrogen, 1 Nitrogen, 

 3 Oxygen. 



34. The general properties of Chondrin are very similar to those of Glutin ; 

 but it is obtainable only from Cartilages, and this after very prolonged boiling ; 

 and it differs from glutin in being precipitated by certain reagents, which have 

 no effect upon the latter. Thus, most acids throw down a precipitate from a 

 solution of chondrin, though this may escape notice on account of the facility 

 with which it redissolves in a slight excess of the acid ; a considerable precipi- 

 tate, however, is thrown down by acetic acid, which is not redissolved by any 

 excess or even by concentrated acid. Chondrin is also precipitated by a num- 

 ber of metallic and other salts, which have no such effect on glutin ; among the 

 most important of these are alum, the sulphates of the protoxide and peroxide 

 of iron, sulphate of copper, acetate of lead, and the nitrates of silver and of the 

 suboxide of mercury. The comparative elementary composition of these two 

 substances is shown in the following table ; from which it appears that, the 

 proportions of carbon and hydrogen being nearly the same in both, glutin con- 

 tains much more nitrogen and less oxygen than chondrin. 



