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684 URINE.
and Hahn have made further observations on dogs with Eck’s fistular
which substantiate this view. In such fistula dogs, they observed that
when meat was fed, violent poisonous symptoms developed which were
almost identical with those produced when carbamate was introduced
into the blood. The same symptoms also appeared on the introduction
of carbamate into the stomach of the fistula animal, while the intro-
duction of carbamate into the stomach of a normal dog had no action.1
As these observers also found that the urine of the dog on which the
operation was made was richer in carbamate than that of the normal
dog, they concluded that the symptoms were due to the non-transforma-
tion of the ammonium carbamate into urea in the liver, and they consider
the ammonium carbamate as the substance from which the urea is derived
in the mammalian liver.
Besides the above view of the formation of urea from ammonium
carbonate and carbamate, which has been called the anhydride theory,
we also have the oxidation theory of Hofmeister.
F. Hofmeister 2
found in the oxidation of different members of
the fatty series, as well as in amino-acids and proteins, that urea was
formed in the presence of ammonia, and he therefore suggests the pos-
sibility that urea may be formed by an oxidation-synthesis. Accord-
ing to him, in the oxidation of nitrogenous substances a radical CONH2,
containing the amide group, unites at the moment of formation with the
radical NH2 remaining on the oxidation of ammonia, forming urea.
Besides the above-mentioned theories as to the formation of urea,
there are others which will not be given, because the only theory which
has thus far been positively demonstrated is the formation of urea in
the liver from ammonium compounds and amino-acids.
The liver is the only organ in which, up to the present time, a forma-
tion of urea has been directly detected;3
and the question arises, what
importance has this urea formation which takes place in the liver? Is
the urea wholly or chiefly formed in the liver?
If the liver is the only organ capable of forming urea, it is to be
expected, on the extirpation or atrophy of that organ, that a reduced
1
Hahn, Massen, Nencki et Pawlow, La fistule d’Eck de la veine cave inferieure et
de la veine porte, etc. Arch, des sciences biol. de St. P<5tersbourg, 1, No. 4, 1892.
In regard to certain differences between the symptoms with carbamate poisoning and
after meat feeding with Eck fistula dogs, see Rothberger and Winterberg, Zeitschr.
f . exp. Path. u. Therap., 1 ; Hawk, Amer. Journ. of Physiol., 21.
2
Arch. f. exp. Path. u. Pharm., 37.
3
In regard to the investigations of Prevost and Dumas, Meissner, Voit, Grehant,
Gscheidlen and Salkowski, and others, on the r61e of the kidneys in the formation of
urea, see v. Schroeder, Arch. f. exp. Path. u. Pharm., 15 and 19, and Voit, Zeitschr.
f. Biologie, 4.
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