126 
Notices of Books. [January, 
much interesting matter. It is important to note that Thudi- 
chum insists on the existence of kreatine in flesh and urine as 
by no means proved, since the processes of its extraction involve 
the transformation of kreatinine into kreatine. The question 
arises, in our mind, whether the phospho-molybdic process 
already mentioned — which is said to produce kreatinine from 
urine free from kreatine — would, when applied to the juice of 
flesh, yield a similar result. 
The chapter on Hippuric Acid affords a strong interest, histo- 
rical, critical, and chemical. The same remark applies to the 
next following chapter, on Indigogen and Urrhodinogen. The 
long and not unamusing controversy on these chromogen pro- 
ducts — or, as their partisans insist on calling them, colouring- 
matters — is here reproduced. The theory that the yellow colour 
of the urine in certain diseases is due to an indigo-bearing sub- 
stance is clearly stated, and still more clearly disproved by Thu- 
dichum. Thudichum demonstrates that the most colourless 
urine — viz., the first urine in the reaction from cholera — yields 
indigo-blue in greatest abundance, and that urrhodine (the red 
matter stated by many to be isomeric with indigo-blue) contains, 
unfortunately for this wild theory, no nitrogen whatever ! 
Passing over the chapters on Pyrocatechin, and the presence 
of phenol and cresol producing substances in the urine, — matters 
still surrounded with mystery, — we come to Schorling’s Omi- 
charyb-oxide, which Thudichum shows to be identical with the 
fallow-resin of Proust, discovered as far back as 1800. Next 
follows a brief description of Urerythrine, also first described by 
Proust as rosacic acid — a pathological ingredient of urine which 
imparts to it a fiery red colour, and is found among the 
“ latentious deposits ” along with the urates. Its speCtrum has 
been specially examined and recorded by Thudichum. 
We now come to Urochrome, “ the matter to which urine 
owes the whole or the greater part of its yellow colour,” — an 
important discovery of Thudichum’s in the year 1864, and for 
which he received the Hastings Prize Medal of the British 
Medical Association. It is impossible to enter into details re- 
lating to this body here ; suffice it to say that the competent 
recognition it has received is fully justified by the mass of sci- 
entific data concerning it. The products of its decomposition — 
uromelamine, uropittine, omicholine, and omicholic acid — are 
also new to chemistry. 
An equally important discovery of Dr. Thudichum’s is krypto- 
phanic acid, first observed by him in 1869. It is a normal con- 
stituent of urine, and the principal one of the bodies “ which 
constitute the complexity of matters formerly called ‘ extrac- 
tives.’ ” The detailed description of this remarkable substance, 
and the abundance of analytical proof concerning it and its 
sixteen studied salts, cannot fail to convince the reader of its 
chemical individuality. The occurrence of acetic and formic 
