The hepatic tissue is liable to a considerable number of different forms of pigmentation.

Icterus is the most frequent and obvious cause of pigmentary infiltration of the liver. We have here to do with hepatogenous icterus, arising from obstruction of the bile ducts. When the bile ducts are obstructed the secretion of bile does not cease, and as excretion is hindered there occurs a re-absorption of the bile. As the hepatic cells lie between the biliary capillaries and the blood, the bile must traverse the former to reach the latter, and consequently the hepatic cells are most immediately and directly stained with the re-absorbed biliary pigment. The pigment at first stains the cells generally, but when the process is prolonged, the bile is deposited in the cells as solid granules, which have a deep brown or greenish colour. The pigmentary deposit occurs chiefly in the central parts of the lobules. The bile sometimes condenses in the biliary capillaries and forms solid plugs or moulds of these.

In the adult the biliary colouring matter, although similar in constitution to haematoidin, rarely forms crystals. In the newly born we have already seen (p. 144) that icterus is associated with a crystalline condition of the pigment. There is some reason to believe that in ordinary icterus neonatorum the pigment is haematoidin of haematogenous origin. The author is able to say, however, that in true obstructive icterus in infants, the pigment forms crystals. He found it so in a case of congenital atresia of the ducts, and in one of obstruction due to thrombo-phlebitis of the umbilical vein.

This biliary infiltration of the liver occurs in consequence of an obstruction either of the main duct (ductus communis) or of the finer ducts in the substance of the organ, as in cases of Cirrhosis and Cancer of the liver, having in that case a partial distribution according to the disposition of the lesion which causes it.

Infiltration with hemosiderin derived from the blood-pigment occurs, as already mentioned, in pernicious anaemia. In Pernicious anaemia there is a reddish brown pigment deposited in the hepatic cells, which may give a general coloration to the organ as a whole. In addition, granules containing iron are present in the liver, and may be detected by the dark green colour which they assume on the addition of* sulphide of ammonium or by the blue colour with ferrocyanide of potassium and hydrochloric acid. (See Fig. 19, p. 72).