The second theory, that the bile is preformed in the blood and separated by the liver, and that jaundice results because of the failure of the liver to perform this office, is no longer entertained, although largely held down to within a very recent period. As the bile acids and bile-pigments are not to be found in the blood, chemistry lends no support to the theory of jaundice by suppression of the hepatic function. As they do not exist in the blood and are found in the secretion of the liver, there can be no other view held than that they are formed by this organ.19
19 The old doctrine of jaundice by suppression, which has always been maintained by Harley (On Jaundice, London, 1863, p. 20 et seq.), has been again restated and strongly advocated by him in his treatise on The Diseases of the Liver, p. 83, which was issued in 1883. In the two following postulates he formulates his view:
"1. The biliary secretion can be actually retarded, and even totally arrested, without alteration of hepatic tissue.
"2. When the liver strikes work and secretes no bile, the animal body becomes jaundiced as a direct consequence thereof."
This view, he affirms, "can be made comparatively easy of absolute proof."
The evidence on which he chiefly relies is exceedingly fallacious. It rests on two facts: the existence of a case of jaundice in which the ducts and gall-bladder contain no bile, but only ordinary mucus; the appearances presented by a liver in a case of jaundice due to obstruction of the common duct. The evidence afforded by the former is entirely fallacious, because in an old case of jaundice with catarrh of the bile-ducts such changes take place in the bile that it loses all of its distinctive characteristics. This may be seen in an ancient example of obstruction of the cystic duct, where the bile which the gall-bladder contained is ultimately transformed into a whitish or colorless mucus. The changes which occur in the so-called cysts of the arachnoid are comparable, and exhibit the entire transformation of blood-pigment, which is closely allied to bile-pigment.
The third theory of jaundice—that which refers the disease to an absorption of the bile into the blood after it has been formed by the liver—is the one now most generally held, and, indeed, as one of the causes is universally held. The bile is absorbed into the blood because an obstacle to its passage by the bile-ducts exists at some point in their course. This is the principal, but not the only, cause of absorption. When the pressure in the vessels falls below that in the ducts, bile will pass toward and into the vessels. Again, it sometimes happens that a considerable part of the bile discharged into the intestines is reabsorbed unchanged, and enters the portal vein and the general circulation, thus causing jaundice.
The disturbances of the liver causing jaundice are various. It sometimes occurs without cause, and the first intimation of it is the peculiar tint of the skin. It is certainly true that powerful emotions are causative; thus, a violent anger has brought on an attack. In such a case we must suppose a depression of the vaso-motor system, and such a lowering of the blood-pressure as to favor the passage of bile into the veins rather than into the bile-ducts. Thus, it has been abundantly shown that a slight difference in pressure will divert the bile in either direction. Heidenhain20 has demonstrated that the bile passes in the direction of least resistance, and in the case of the considerable vaso-motor depression caused by extreme emotion the least resistance is in the direction of the vessels. More frequently than moral emotion is catarrh of the bile-ducts. It is not necessary for the catarrhal swelling of the mucous membrane to close the ducts to have the bile pass into the veins; such a degree of swelling as to make the passage of the bile somewhat difficult suffices. A simple hyperæmia of the mucous membrane may cause sufficient obstruction of the bile-ducts to give rise to jaundice. Gastro-intestinal catarrh plays an important part in the production of simple jaundice. Frerichs21 ascertained that of 41 cases, gastro-duodenal catarrh existed in 34. Ponfick22 considers catarrh of the ducts the principal factor. In fact, at the present time there is but one dissenting voice on this point.23
20 Quoted by Legg, supra, p. 253.
21 Diseases of the Liver, Syd. Soc. ed., by Murchison.