A large proportion of the fibrine formers are changed in passing through
the liver (Lehmann, Bernard), in man as much as 2,690 grammes daily
(Brown Sequard), a fact which goes to account for the increase of
fibrine in inflammation when the liver is inactive. The change consists
mainly in deoxidation and reduction into simpler compounds which can be
more readily dissolved and eliminated. Arrest of the liver functions in
fever is therefore liable to throw into the blood, products that are
little soluble and often poisonous. The end product is largely urea, and
this Cyon always found in excess in the hepatic veins of dogs (in the
portal veins 0.08 grammes, and in the hepatic veins 0.14 to 0.17
grammes). In man hepatic disorder is at once marked by the lessening or
disappearance of urea from the urine, and the increase of the less
oxidized uric acid (Parkes). In acute atrophy of the liver, urea
disappears from the urine, being replaced by the less oxidized leucin
and tyrosin (Frerichs, Murchison). In birds urea is replaced by uric
acid and this is always found in the liver.
The increase of urea and allied products bears a direct relation to the
activity of the hepatic circulation. Stimulation of the liver by
electric current sent through the abdominal walls largely increased the
secretion of urea (Sigrist, Stolnikow, Schröder and Salomon). Murchison,
Perrin and Bruardel had a great increase of urea by stimulating the
circulation in the liver. Certain agents ingested are transformed into
urea, among which may be named glycocolle, brucin, asparagin, sarcine,
alanine, and ammonia muriate.
Any degeneration of the hepatic cells which impairs or arrests their
functions lessens the production of urea. In fevers therefore and in
hepatic degenerations the extent of the functional or structural
derangement may be to a large extent gauged by the diminution of urea. A
simple hyperæmia, without as yet any serious impairment of structure or
function, may be attended by a marked increase of urea, whereas any
destruction of the liver cells, or any serious modification which
interferes with the normal function, brings about a decided decrease. A
hepatic disorder accompanied by suppression of urine is always a grave
disorder. On the contrary a free secretion of urine during liver disease
is a favorable symptom.
There is reason to believe that red blood globules are destroyed in the
healthy liver, producing bilirubin and urea (Landois). In diseased
states this becomes excessive, and the resulting coloring matter is
often modified, giving the strong tints, seen in the urine in fever and
certain hepatic disorders.