It was formerly thought that the liver varied inversely as the size of the animal but Magnan[23] and others have shown that the matter is not so simple. In the first place if there be an actual mathematical formula it is that the liver varies in size inversely as the surface area of the body, but this is not the whole story. It seems that the relation of size of the organ to its weight is not constant and that it is better to judge of the organic capacity by the latter. In herbivorous animals, both birds and mammals, the liver is lightest per kilo of body weight; next in weight are in order, fisheaters, meateaters, insectivora, seedeaters, fruiteaters and omnivora. There is besides this a roughly inverse ratio between the size of the liver and the length of the intestine and in the class Aves inversely as the size of the lungs also. From the immediately foregoing statements it is apparent that a bewildering variation occurs and that only rough measurements of the relative volume of the liver are available. An attempt was made in the Marsupialia, which present all the variations given, to discover if any peculiar pathology corresponded with the above groups; as it was fruitless, no change from our zoological treatment will be made. Lobar arrangement varies from the relatively simple double avian type to the manifold lobulations of the seal or the marsupial but I can find no literature to indicate that lobes or lobulations have a direct effect upon functions. There must be a difference of blood supply for in certain infectious diseases like enterohepatitis and amœbiasis, the cystic and extreme right lobes are more affected than the left parts of the organ. In the bird this is not so difficult to follow since the three divisions of the portal vein, while they combine at times in an ampulla within the hilum of the liver, seem directed to certain lobes, that from the left portal seeming to point toward the right side. The avian portal system differs from the mammalian in having a large branch from the renal area, the so-called renal-portal system, pass to the liver, and by having a free anastomosis between the portal area and the caudal vena cava whereby blood from the pelvic district may pass into the general circulation without going through the liver. There is no unanimity of opinion as to the function or importance of this connection[24] and from the data collected here there is no peculiar renohepatic pathology.