396 DERIVATIVES OF THE PROTEIN-COMPOUNDS. 



which has been softened in water, and deprives it of the property 

 of gelatinising on cooling. 



The only compound which has been carefully studied is that 

 which it forms with tannic acid. This has been done by Mulder, 

 who finds that, when freshly precipitated, it is white and curdy, 

 when dried it is hard, brittle, and pulverisable, and that it is inso- 

 luble in water and alcohol. If the glutin is precipitated with an 

 excess of tannic acid, we obtain a combination of equal equivalents 

 of glutin and tannic acid^C^H^N^ + CigHyOn ; if, on the 

 other hand, there be an excess of glutin, the precipitate consists 

 of 3 equivalents of glutin and 2 equivalents of tannic acid 

 =C 39 H 30 N 6 I5 + C 36 H 14 22 . 



No combinations of glutin with alkalies, earths, and pure 

 metallic oxides are as yet known. Caustic lime dissolves in a solu- 

 tion of glutin. Glutin can, however, combine with several basic 

 salts; a very considerable quantity of freshly precipitated bone- 

 earth dissolves in a solution of glutin. Solutions of glutin, when 

 treated with alum and with sulphate of peroxide of iron, do not 

 yield a precipitate, except on the addition of an alkali ; the preci- 

 pitate in this case consists of glutin and a basic salt=Al 2 O 3 .SO 3 

 or Fe 2 O 3 .2SO 3 . The precipitate obtained with sulphate of the 

 binoxide of platinum appears to contain basic sulphate of binoxide 

 of platinum=PtO 2 .SO 3 . 



Physiological Relations. 



Occurrence. Haller's remark : Dimidium corporis humani gluten 

 est, now requires to be modified to the assertion that half of the 

 solid parts of the animal body are convertible, by boiling with tvater, 

 into gelatin; for actual gelatin is not contained in the animal 

 organism. It has been for a long time maintained that gelatin is 

 an actual constituent of the swimming bladder of certain fishes ; 

 but even this is by no means probable. 



The tissues of the human body have been divided into the 

 gelatigenous and the albuminous. Appropriate as such an arrange- 

 ment might at first sight appear, it is opposed by the experience 

 both of chemists and anatomists ; Berzelius and E. H. Weber 

 assert that as the permament cartilages are not converted by 

 boiling with gelatin, and as moreover they cannot be regarded as 

 albuminous, cartilages must be divided into the gelatigenous and 

 non-gelatigenous, and thus these observers abandon the old division 

 of the tissues. Miiller has subsequently devoted much attention 

 to the structure and constitution of cartilage, and he finds that the 



