As said in the beginning of this paper, I believe, the pathology of jaundice may be embodied under the two heads, jaundice from suppression of the biliary functions, and jaundice from re-absorption of the secreted but retained bile. These are at best, however, but vague terms, and in order to make the pathology of jaundice somewhat more definite it will be necessary for me to subdivide these two great classes in the following manner:—
(CLASS A.)—JAUNDICE FROM SUPPRESSION.
Arising from:—
(1) Enervation.
(2) Disordered hepatic circulation.
(3) Absence of secreting substance.
(CLASS B.)—JAUNDICE FROM RE-ABSORPTION.
Arising from:—
(1) Congenital deficiency of bile-ducts.
(2) Accidental obstruction of bile-ducts.
I shall now try to point out the pathology of these different states, and see how far they are able to explain the occurrence of jaundice under the various conditions already alluded to.
JAUNDICE FROM SUPPRESSION.
Although there can be no misunderstanding the meaning of the term "jaundice from suppression," there may, nevertheless, be some difficulty in comprehending how the skin becomes yellow, and the urine high coloured, when the secretion of bile is arrested. In order to explain how this occurs, it will be necessary to recall to mind what was said regarding the nature of the biliary secretion. It will be remembered that I began by saying, that while some of the constituents of the bile are generated in the liver itself, there are others that exist, pre-formed in the blood.
If this view of the physiology of the biliary secretion be correct, it is perfectly evident that when the secretion of bile is arrested, those substances which the liver generates will be entirely wanting, while those which it merely excretes from the blood will accumulate there as soon as their excretion is prevented; just as urea accumulates in the circulation when its elimination by the kidneys is stopped. Hence it is that, as soon as the biliary secretion is in abeyance, biliverdine accumulates in the blood (until the serum is as it were completely saturated with the pigment), from which it exudes and stains the tissues, and produces the colour we term jaundice. At the same time, or even before the skin becomes yellow, the urine assumes a saffron tint in consequence of the elimination of the colouring matter by the kidneys.8 From this it will be seen that I regard the yellow skin and high-coloured urine of jaundice as simply due to the deranged secretion of biliverdine, quite independent of the presence or absence of the other constituents of the bile, the effects produced by which will be referred to elsewhere. Meanwhile we shall separately consider the further pathology of the three subdivisions of jaundice arising from suppression.
8 The true order of the occurrence of these changes is:—On the second day the urine becomes high-coloured; in a day or two later the skin assumes a yellow tint; and, in very severe cases, within the first week or two, the sweat, the milk, the tears, the sputa, and the serum in the thoracic and abdominal cavities, become of a more or less decided yellow hue.