DR. PROTIT ON ANIMAL CHEMISTRY. 615 
tion, is not raised to the blood standard, and consequently, being 
unfit for the future purposes of the economy, is, agreeably to a 
law of the economy, ejected through the kidneys; but these 
organs, instead of dismerorganizing it as usual—that is to say, 
instead of converting it into the lithate of ammonia—permit it to 
pass unchanged. That this is a just view of the matter, cannot, 
I think, be doubted ; for if the chyle was properly converted into 
blood, this fluid, and not chyle, ought to be thrown off by the 
kidneys. On the other hand, it may be stated as an argument 
in favour of the notion that the kidneys are affected, that I have 
often found chyle in the blood when the urine was entirely free 
from albuminous matters; shewing that, in the healthy state of 
those organs, even though chyle does get into the sanguiferous 
system, it is not necessarily ejected, or, if it is, that it undergoes 
the usual changes in passing through the kidneys. This affection 
of the kidneys, however, like that in diabetes, does not seem to 
amount to organic disease, at least such as is cognizable by the 
senses. 
The next principle occurring in the urine, on the properties of 
which I shall make a few remarks, is urea . This principle, of 
which I here exhibit a specimen, has been lately found in the 
blood. Indeed I detected it, or something very similar, in the 
blood myself, fourteen or fifteen years ago, but could not at that 
time believe the evidence of my senses. It has been lately said 
to have been formed artificially, but I have some doubts on this 
point, at least as to the manner stated. 
Urea I consider as .an albuminous product, and one of two 
principles into which that substance is capable of being decom¬ 
posed, as I hope at some future time to be able to demonstrate. 
It plays a very important part in the urine, chiefly of a secondaiy 
nature, and which admits of a complete and satisfactory expla¬ 
nation, founded on its composition. I ascertained, many years 
ago, that it is composed of the elements of carbonate of ammonia 
and water: and hence the ease with which it is changed into these 
principles by a variety of substances, particularly by the fixed 
alkalies and alkaline earths, which, seizing the elements of car¬ 
bonic acid, set the ammonia free. To the decomposition of this 
principle is, therefore, chiefly owing an ammoniacal state of the 
urine, one of the most distressing conditions of this secretion, 
and one of the most liable to terminate in the formation of stone 
in the bladder. 
Urea occurs as a natural ingredient in healthy urine, but some¬ 
times in much greater quantity than usual; in which case it may 
be readily detected by the addition to the urine of a little pure 
