178 



NORMAL ANATOMY OF THE LIVER. 



the gall-bladder contains bile, and the mucous 

 membrane becomes rugous and reticulated. 

 At the eighth month, and during the ninth and 

 tenth months, the liver becomes still more ho- 

 rizontal in position and of a deep red colour. 

 The bile is more abundant and of a clear green 

 tint. At the tenth month, that is, at birth, the 

 relative proportion of the liver to the rest of 

 the body is as 1 to 18 or 20; the average in 

 the adult being as 1 to 36. After birth the 

 size and weight of the liver diminish until the 

 end of the first year, for, according to Meckel, 

 the liver of the newly born infant weighs one- 

 fourth heavier than at the age of eight or ten 

 months. The borders of the liver are rounded 

 in the foetus, and the inferior surface is convex. 

 The lobes are nearly equal until birth, after 

 which the left diminishes in size, the right re- 

 maining stationary or growing but little, and 

 at the age of one year the left lobe is scarcely 

 one-half so large as at birth. The texture of 

 the liver in the foetus is soft and fragile and 

 apparently homogeneous in structure; during 

 the earlier periods its colour is a light brownish 

 grey ; at about the mid-period it becomes 

 deeply red, and after birth loses a portion of 

 its colour from a diminution of the quantity of 

 blood circulating through it. 



Uses of the liver. The liver performs two 

 most important functions in the animal eco- 

 nomy: 1, it separates from the venous blood 

 of the chylopoietic viscera certain elements 

 which are needful to digestion ; and, 2, it de- 

 purates the venous blood. The first of these 

 functions constitutes the secretion of bile. 

 The second is evinced in a comparative exami- 

 nation of two of the great depurating organs, 

 the lungs and the liver, in the various classes 

 of animals, where the latter will be constantly 

 found in exact relation with the development 

 of the respiratory organ, and with the neces- 

 sity for the removal of a larger quantity of 

 hydrogen and carbon from the blood. Thus, 

 in herbivorous animals, the liver is small ; it is 

 small also in monkeys and in man. It is large, 

 and has reached its highest development 

 amongst Mammiferous animals in Carmvora. 

 In birds it is larger in proportion than in Car- 

 nivora, from the greater necessity of a highly 

 oxygenated blood in that class of animals. 

 In Reptiles, with cold blood and a low degree 

 of respiration, it is large; it is large also and 

 for the same reason in Fishes; and very large 

 among the Invertebrata. 



Secretion of bile. The bile, which would 

 appear, from the existence of follicular recesses 

 in the alimentary canal, to be produced in all 

 animals from the lowest to the highest, is 

 secreted in man and in vertebrata from the 

 blood during its circulation through the lobu- 

 lar venous plexus in the lobules' of the liver. 

 Hence it becomes a question of importance to 

 physiology to decide from what kind of blood 

 it is eliminated. If, according to Kiernan, all 

 the arterial blood of the hepatic artery become 

 venous previously to its passage into the lo- 

 bular venous plexus, the bile must be secreted 

 from venous blood ; that venous blood being 



derived from the capillaries of the chylopoietic 

 organs, and from the capillaries of the hepatic 

 artery. I have given Kiernan's reasons for the 

 belief that this is the truth ; and in corrobo- 

 rating the results of his injections I must also 

 add my own testimony to his view of the se- 

 cretion of the biliary fluid. Muller, enter- 

 taining, as I have already shewn, a different 

 opinion with regard to the distribution of the 

 vessels of the liver, believes that the bile is 

 secreted from a mixed arterial and venous 

 blood, resulting from the termination of both 

 the hepatic artery and portal vein in the " vas- 

 cula ultima reticulata," or lobular venous 

 plexus. From the undecided manner in which 

 he expresses this opinion, I am tempted to 

 give the quotation in which it is contained, 

 that my readers may judge how far he be really 

 in earnest in his assertion. " It is known that 

 injection thrown either into the hepatic artery 

 or into the portal vien, fills the same capillary 

 net-work, from which, on the other hand, the 

 hepatic veins likewise arise." 



Since reading the above paragraph I have 

 injected twelve livers for the purpose of de- 

 ciding the question, in my own mind, of the 

 ultimate termination of the hepatic artery; but 

 I have in no instance succeeded in forcing in- 

 jection into the lobular venous plexus, although 

 every other part of the organ has been beauti- 

 fully injected. I have therefore been forced to 

 the conclusion that some mistake must exist 

 with regard to this passage, and that, although 

 perfectly true when confined to the portal vein, 

 Muller cannot mean that the capillary net- 

 work (lobular venous plexus) from which the 

 hepatic veins arise, is actually filled from the 

 hepatic artery. But he continues, " It ap- 

 pears, therefore, that the arterial blood of the 

 hepatic artery, and the venous blood of the 

 poita, become mixed in the minute vessels 

 of the liver, and that the secretion of bile 

 probably takes place from both." Now, with 

 deference to Miiller's judgment, the question, 

 with our present knowledge upon the exact 

 anatomy of the liver, ought not to be one of 

 probability or surmise; does it? or does it not? 

 But he appears far from satisfied, in relying 

 for the support of his argument upon his own 

 peculiar theory of the arrangement of the he- 

 patic vessels, and, as if distrusting its effici- 

 ency, he exclaims in another page of his Phy- 

 siology, " But the possibility of bile being 

 secreted from arterial blood is demonstrated 

 by the cases in which the vena portce enters the 

 vena cava directly instead of being distributed 

 through the liver. Mr. Abernethy observed this 

 anomalous structure in a male child ten months 

 old ; and Mr. Lawrence has detailed a case in 

 which the same malformation existed in a child 

 several years of age. In Mr. Abernethy's case 

 however the umbilical vein was still pervious 

 and branched out in the substance of the liver; 

 it is possible therefore, as Mr. Kiernan remarks, 

 that the arterial blood, after having nourished 

 the liver, was poured into the branches of the 

 umbilical vein, just as it is in the normal con- 

 dition, according to his opinion, poured into 



