62 PRINCIPLES OF ANIMAL NUTRITION. 
is accordingly equivalent to a gain of 76.5 parts of carbon, and con- 
versely, if it be shown that the body has gained one part of carbon 
in the form of fat, this is equivalent to a gain of 1+0.765=1.307, 
or, in round numbers, 1.3 parts of fat. Benedict & Osterberg’s 
average corresponds to the factor 1.314. 
Protrin.—As in the case of the food, the term protein is used. 
to signify the whole mass of nitrogenous material in the body, in- 
cluding, besides the true albuminoids, the collagens or gelatinoids, 
the keratin-like bodies, the nitrogenous extractives, etc. 
Neumeister * gives the following figures for the elementary 
composition of the simple albuminoids: 
Minimum, | Maximum, Average, 
Per Cent. Per Cent. Per Cent. 
Carbon ............. 50 55 52 
Hydrogen............ 6.5 7.3 7 
Nitrogen............. 15 17.6 16 
FOXYZEN.. eee e cece eee 19 24 23 
Sulphur.............. 0.3 2.4 2 
100 
Some of the compound albuminoids, particularly the nucleo- 
albuminoids, do not vary greatly in composition from the above 
figures, while others notably the mucins, which contain a carbo- 
hydrate group, show a higher percentage of oxygen and less carbon 
and nitrogen. 
The gelatinoids, likewise, do not differ greatly in composition 
from the albuminoids. For collagen, Hofmeister + found the fol- 
lowing averages: 
Carbon: chick iiwecesitoouang a elwuaeen 50.75 
Fy Crogen were cana ee ako S emcee iene 6.47 
INIEROBEN Are seine vaca aye at ny setae anand 17.86 
Oxygen 
a disrlb pute Riba Seat lagaceoa ee eee 24. 
Sulphur ; ise 
100.00 
Keratin is distinguished by a relatively high proportion of 
sulphur (3 to 5 per cent.), but otherwise, according to Neumeister, { 
does not differ materially in composition from the true albuminoids. 
* Lehrbuch der Physiol. Chem., p. 22. + Zeit. physiol. Chem., 2, 322. 
} Loc. cit., p. 493. 
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