THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL. 501 



The liver more especially elaborates bile and sugar. It secretes the bile at 

 the expense of the blood of the portal vein, which comes from the intestinal 

 tunics charged with assimilable substances absorbed by the veins of the villi. 



The bile is, therefore, in this respect an excrementitious secretion ; though 

 all its elements are not excreted, some of them acting on the alimentary 

 substances, and others being absorbed. From the most recent researches, it 

 would appear that it has a share in the purification of the blood, in digestion, 

 and in calorification — in the latter especially, as its absorbed elements are very 

 rich in carbon and hydrogen, bodies eminently fitted for the production of 

 animal heat. 



The liver is also a glycogenetic gland, this function having been demon- 

 strated to pertain to it by Bernard. The sugar formed in the hver finds its way 

 into the blood, and leaves the organ by the sublobular veins. It is elaborated in 

 the hepatic cells, by the transformation of the substance known as " animal 

 amidon," which is brought into contact with a kind of diastaste that exists with 

 it in their interior. 



It will thus be seen that the liver furnishes two very different products — bile 

 and sugar. The knowledge of this fact, combined with the internal arrangement 

 of the organ, has led some anatomists to consider the organ as two glands 

 reciprocally contained within each other. According to them, one gland is 

 tubular, and formed by the system of biliary ducts — this gland secretes the bile ; 

 the other gland is constituted by the hepatic cells, which produce the sugar. But 

 this hypothesis should be rejected, for it is probable that the sugar and bile are 

 produced in the large hepatic cells, and that the first passes into the veins, while 

 the second is poured into the biliary ducts. 



In Solipeds, the secretion of bile, though most active during the digestive 

 period, yet goes on in a continuous manner. 



(Certain deductions of a pathological kind are based upon the foregoing 

 anatomical facts, and have an important bearing with regard to comparative 

 pathology. They have been pointed out by Wilson, and are as follows : Each 

 lobule is a perfect gland ; its structure and colour are uniform, and it has the 

 same degree of vascularity throughout. It is the seat of a double venous 

 circulation ; the vessels of the one — hepatic — being situated in the centre of the 

 lobule, and those of the other — portal — at the circumference. Now, the colour of 

 the lobule, as of the entire liver, depends chiefly on the proportion of blood 

 contained within these two sets of vessels ; and so long as the circulation is 

 natural, the colour will be uniform. But the instant that any cause is developed 

 which will interfere with the free circulation of either, there will be an immediate 

 diversity in the colour of the lobule. 



Thus, if there be any impediment to the free circulation of the venous blood 

 through the heart or lungs, the circulation in the hepatic veins will be retarded, and 

 the sublobular — or supra-hepatic — and intra-lobular veins will become congested, 

 giving rise to a more or less extensive redness in the centre of each of the 

 lobules ; while the marginal or non-congested portion presents a distinct border 

 of a yellowish white, yellow, or green colour, according to the quantity or quality 

 of the bile it may contain. " This is ^passive congestion ' of the liver, the usual 

 and natural state of the organ after death ; " and as it commences with the 

 hepatic vein, it may be called the first stage of hepatic venous congestion. 



But if the causes which produced this state of congestion continue, or be from 

 the beginning of a more active kind, the congestion will extend through the 



