Dr. Schunck on the Occurrence of Indigo-blue in Urine. 291 
resembling indican seemed indeed exceedingly probable, since 
the same reagents which produce indigo-blue from indican lead 
in most cases to the development of the blue colour in particular 
kinds of urine. The extreme rarity, however, of these kinds of 
urine appeared to present an insuperable obstacle to the further 
investigation of the subject, and I therefore resolved to ascertain 
whether any conclusions could be arrived at from an examination 
of ordinary healthy urine. 
When muriatic or sulphuric acid is added to urine, the mix- 
ture on being heated becomes brown and begins to deposit dark 
brown flocks, which increase in quantity when the heating is 
continued. When these flocks are filtered off, washed and dried, 
they form a compact dark brown mass, from which cold alcohol 
extracts a resinous matter, leaving undissolved a brown powder, 
which dissolves, however, in a boiling mixture of alcohol and 
ammonia, ‘This powder contains nitrogen, and so much re- 
sembles indifuscine, one of the products of the decomposition 
of indican, as almost to lead one to suspect their identity. Its 
composition, however, though it stands, as I have ascertained, 
in a certain relation to that of indigo-blue, is quite different 
from that of indifuscine. Now if the liquid filtered from these 
flocks be mixed with a salt of oxide of copper and an excess of 
caustic soda, it becomes greenish, and if after being filtered it be 
heated for some time, it gradually deposits a tolerably large 
quantity of suboxide of copper, which is a proof of the presence 
of sugar. That the latter has been formed during the process 
and did not pre-exist, may be ascertained by previously heating 
a portion of the urine with a’salt of copper and caustic soda, be- 
fore treating the remainder of it with acid. Samples of urine, 
which, when tried in this way, afforded very doubtful or no 
indications of their contaming sugar, were found, after being 
boiled with acid, then filtered and made alkaline, to reduce oxide 
of copper in a very marked manner. This reaction, which is so 
simple that it is only surprising it should never before have been 
observed, seems to me to prove that there is contained in urine 
some body, which by decomposition with acids yields sugar, the 
brown flocks precipitated at the same time being probably the 
substance with which the sugar was originally associated in the 
form of a copulated compound. From various considerations, 
which I need not detail, | was led to infer that this body could 
be no other than the very imperfectly known, so-called extractive 
matter of urine, and I accordingly commenced an investigation 
of this substance, which has led to conclusions of considerable 
interest. On discovering that the composition of the brown 
flocks formed by the action of strong acids on urine is expressed 
by the formula C4 H7 NO*, which is also that of anthranili¢ 
U2 
