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CHAPTER V. 



DISEASES OF THE LIVER, SPLEEN, AND PANCREAS. 



IN the human being the liver is the largest gland in the body, weighing, according to some 

 authorities, from ij Ib. up to 4| Ib. ; according to others, from forty to fifty-five ounces. In the 

 canine subject it is even larger >n proportion, and probably also proportionately more 

 important. 



In man the liver has five lobes or portions, and in the dog we also find five principal 

 lobes, in a depression in the middle lobe of which we find the gall bladder. This receptacle of 

 bile ends in the ductus choledochus, or bile duct, which, along with the smaller efferent duct 

 of the pancreas, enters the duodenum, at from one to five inches (according to the size of the 

 dog) from the pyloric opening of the stomach. 



The pancreas of the dog is much more elongated than that of the human being ; it pours 

 the principal portion of its contents into the duodenum, an inch or two beneath the opening 

 of the bile duct. 



The spleen of the dog deserves no special mention here. As to the enormous gland 

 called the liver, its value in the animal economy can hardly be over-rated. All the blood 

 of the body passes through it. The arterial blood that is distributed to other portions of the 

 body, such as the head, the fore-legs and hind-legs, &c., having performed its life-giving functions, 

 is taken up by the veins and carried back to the heart directly. Not so, however, with the 

 blood that has been arterially distributed to the intestines. This does not go back at once to 

 the heart ; it is taken up by a series of capillary veins, which unite to form the portal vein, 

 and this vein enters and is spread out in the tissue of the liver around the cells of that gland, 

 and from this blood and by this gland, the liver, the bile is secreted, which is to perform such 

 an important function in the process of digestion. 



Now the bile ducts carry off this secretion, which has been either extracted from the 

 blood or formed in the cells, from the blood of the portal veins ; carry it off and pour it into 

 the gall bladder, or reservoir for the bile ; the blood itself is then taken up and returned 

 into the inferior vena cava, and so sent on to the heart. We have seen water diverted from a 

 river to form some distant mill-dam, and, after it had done its work for the mill, returned 

 again by another channel. This gives us, in a rude fashion, some idea of the economy of the 

 portal system. 



We need not here discuss the question as to whether bile exists to a certain extent 

 ready made in the blood, and is simply separated from it by the liver ; or whether the 

 hepatic cells positively manufacture the bile, although we incline to the former theory. 

 Neither need we occupy space by describing the chemical constituents of this curious fluid. 

 Suffice it for us to know that bile is the product of the liver, and is of the highest importance 

 to digestion. It is a yellow oily-looking fluid, with an extremely bitter taste. It is essentially 

 of a soapy nature, and its uses are supposed to be (i), to destroy or neutralise the acidity of 

 the chyme which has been derived from the gastric secretions ; (2) to aid the pancreatic juice 

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