e 
DIGESTIVE SYSTEM. 317 
have no proof that these substances are derived from any 
other source than the food. Hence, for the supply of this 
single secreted fluid, substances containing, at least, these 
eight elementary bodies, must be obtained for the use of 
the system. It would be difficult to determine which of 
these substances could be spared, so as to produce the least 
injurious alteration in the secretion ; but it is obvious; that, 
as they all occur constantly; they are all necessary to the per- 
fection of the secretion and the healthy state of the system: 
As animal matter contains a great deal of azote, physio- 
logists have differed in their opinion with respect to its ori- 
gin, some attributing its source to the air in respiration, 
others to the food. M. F. Macenpte instituted a series 
of experiments, for the purpose of determining this ques- 
tion.. He selected a dog in good condition; three years old, 
and fed him with substances which contained no azote: 
These consisted exclusively of white sugar and distilled 
water. During the first week he appeared to enjoy his 
new regimen, but in the second week he began to grow 
lean, his eyes became ulcerated, and gradually losing 
strength, he died on the thirty-second day. The urine was 
found to be alkaline, and to present no trace of uric or 
phosphoric acid. The bile resembled that of herbivorous 
animals, and the excrements contained but a small propor- 
tion of azote. In the body the fat had disappeared, the 
muscles were reduced in size, and the volume of the intes- 
tines diminished. Similar results were obtained, when the 
experiment was repeated upon two other dogs ; and like- 
wise in two cases when olive oil, and in others, when gum 
was substituted in place of sugar *. 
pee Dd Ly oye pele SOR gl Meg) ee Pe ap! ge 
* Precis Elementaire de Physiologie, Paris 1817, 2 vols. S8vo. ii 
p: 390,—394, 
