Constitution of Gelatine and its Transformations. 75 
relations, the part which it performs in nutrition, and the modes 
of its assimilation are unknown. 
Before proceeding to the subject proposed, it will be well to 
Lok recall some of the characteristics of the different nitrogenous or- 
1 ganic compounds, which are divided into two widely dissimilar 
ha groups. ‘The first of these comprises all of those substances 
ea generally known as the proteine compounds, gelatine, chondrine, 
F the organic alkaloids, both natural and artificial, a number o 
( azotized acids and some other principles, as amygdaline and aspar- 
z ine. These are characterized by evolving ammonia when de- 
i composed by heat, especially when in the presence of an alkaline 
; base, and often by the action of acids and alkaline solutions. 
Many of them are artificially formed from substances which do 
hot contain nitrogen, and the mutual relations are then such that 
the azotized bodies may be derived from them by the addition of 
the elements of ammonia and the abstraction of those of water, 
so that NH,, NH, or sometimes N only, may be regarded as re- 
placing one, two or three equivalents of oxygen; this reaction is 
often effected by the direct action of ammonia upon. the organic 
Substance. Irom these considerations we are led to regard the 
he first class by the appellation of nitrids. In these compou 
be regarded as replacing an equivalent of hydrogen or 
perhaps the residue NHO, - 0, = NHO, is sub- 
From the large amount of oxygen which these 
odies contain, they do not yield ammonia when decomposed ; 
he 
h hydrogen and are converted into ammonids with the 
Bi The analyses of gelatine prepared in different ways and from 
different ea show i cobsanoiabla variation in the propor- 
fons of its elements. The following are taken from Mulder’s 
Physiology, p. 307, Am. Ed. ? 
