188 THE CAT. [CHAP. vi. 



vessels, and in the areolar tissue. The portal veins end by minute 

 vessels, which surround and penetrate the lobules of the liver 

 (whence they are called interlobular veins), while the hepatic ducts 

 end in most delicate canals, which pass amongst the hepatic, or 

 liver, cells, which make up the substance of the lobules between 

 its multitudinous vessels. 



The blood being thus conveyed to the circumference of each 

 lobule, proceeds thence to its centre, where it collects in the com- 

 mencements (ultimate twigs) of the hepatic vein which, from the 

 fact that they thus take origin, are called intra-lobular veins. 



The liver cells (or hepatic cells) form the secreting substance of 

 the liver, and are spheroidal or polygonal nucleated bodies of a 

 yellowish colour, containing granules and fatty matter besides the 

 nuclei. They vary from -g-J to --O'TTT of an inch in diameter. 



The FUNCTION of the liver consists in the secretion of bile, 

 though the full meaning and effect of its activity is not by any 

 means entirely understood. 



BILE is an alkaline, greenish-yellow, viscid, bitter fluid, containing 

 from 8 to 16 per cent, of solid matter, consisting principally of a 

 compound nitrogenous substance termed Ulin. It also contains a 

 non-nitrogenous substance called cholesterin, with certain salts and 

 peculiar colouring matters (biliverdin and bilifulvin) containing iron. 

 These colouring and other substances are formed by the cells of the 

 liver, and do not pre-exist in the blood. 



Another substance which is found accumulated in the liver after 

 death, does not escape by the hepatic ducts. This is glycogcn or 

 animal starch. 



The rapidity with which bile is secreted varies according to 

 circumstances, increasing during the process of digestion. 



The bile does not all pass directly into the intestine, but part of 

 it regurgitates along the cystic duct into the gall-bladder, where it 

 may remain for a certain time, and where it becomes somewhat 

 thickened. 



The action of the bile on the food is, in the first place, to neutra- 

 lize the acid of the chyme, and secondly, to aid in emulsifying 

 fatty matters. 



But in addition to its effect on food, the secretion of bile is 

 important as a mode of eliminating from the body substances, the 

 removal of which is necessary to healthy life. The colouring 

 matters of the bile arc always entirely excreted, but other of its 

 constituents appear to be decomposed in the large intestine, their 

 nutritious matter being re-absorbed and their refuse driven on as 

 excretin, stercorin and some other substances. 



Yet other functions are performed by the bile, namely, that of 

 exciting, directly or indirectly, the action of the intestinal mucous 

 membrane and also the peristaltic action. 



It is also said to have an anti-putrescent action on the food, 

 putrefaction taking place in the alimentary canal in the absence 

 of bile. 



