46 PRINCIPLES OF ANIMAL NUTRITION. 
Pfeiffer & Eber,* have shown with a high degree of probability 
that the pentoge carbohydrates of the feed have some connection 
with the production of hippuric acid. The former investigators 
observed a marked increase in the production of hippuric acid by 
a sheep after the administration of cherry gum (impure araban) and 
of arabinose, and the latter obtained the same effect, although in a 
less marked degree, by feeding cherry gum to a horse. They also 
call attention to the differences in the behavior of the pentose carbo- 
hydrates in the organism of the herbivora and in that of man and 
the carnivora, but do not attempt to give a final solution of the 
problem of the origin of the hippuric acid in the former case, while 
they freely admit that it is difficult, if not impossible, to explain 
some of the facts already on record on the hypothesis that the pen- 
toses are the chief source of hippuric acid. 
CREATIN AND CREATININ.—Among other nitrogenous constit- 
uents of the urine of man and the carnivora may be mentioned 
creatinin. This body is the anhydride of creatin, and the two 
together constitute the principal part of the so-called flesh bases 
which are contained in considerable quantity in muscular tissue. 
When meat is consumed, its creatin is converted into creatinin and 
excreted quantitatively in the urine, the creatinin content of which 
may be thus considerably increased. As to the physiological signifi- 
cance of the creatin of muscular tissue opinions are divided, but 
good authorities are inclined to regard it as an intermediate 
product of the metabolism of the proteids which is ultimately con- 
verted into urea, and to urge that the fate of creatin taken into the 
-stomach is not necessarily the same as that of the creatin produced 
in the muscles. 
Aromatic Compounps.—Besides the benzol radicle of hippuric 
acid, small amounts of other aromatic compounds are also found in 
the urine. These bodies, belonging chiefly to the phenol and indol 
groups, owe their origin exclusively to the putrefactive processes 
already mentioned as taking place in the intestines, and are found in 
the urine almost entirely in combination with sulphuric acid as the 
so-called conjugated sulphuric acids, so that the amount of the 
latter is employed as a measure of the extent of these putrefactive 
processes, 
* Landw. Vers. Stat., 49, 97. 
