760 SPECIAL PHYSIOLOGY. 



found to open into the inferior vena cava, and yet bile has been se- 

 creted. Hence the portal blood has been held to be non-essential to 

 the formation of bile ; but, in such cases, the umbilical vein is per- 

 meable, and sends branches through the liver; moreover, the blood of 

 the hepatic arteries, having first become venous, may enter the tabu- 

 lar plexuses, and so secrete the bile. 



That the biliary acids are not preformed in the blood, but are elab- 

 orated in the hepatic cells, is shown by extirpating the liver in frogs; 

 these animals then survive for some days, and yet no trace of the 

 fatty acids of the bile is found in the blood, which would be the case, 

 if the bile were preformed in, and merely separated as an educt from, 

 that fluid. The green coloring matter, and also cholesterin. may, 

 however, pre-exist in the blood. The cholic acid may be derived from 

 the fats of the blood, whilst the taurin and glycocoll, which are con- 

 jugated with it, the former containing both sulphur and nitrogen, and 

 the latter only nitrogen, probably arise from the decomposition of al- 

 buminoid substances. The coloring principles may be formed from 

 the cruorin, or coloring matter of the blood, which they closely resem- 

 ble. Animals fed on fat, have been said to secrete proportionally 

 more bile; but this is denied, and the quantity of albuminoid food 

 consumed, seems rather to regulate the amount of this secretion. 



Besides its office in digesting fat, and stimulating the muscular acts 

 concerned in digestion and absorption, the bile has other uses. The 

 fatty acids, largely reabsorbed, may become converted, in the circula- 

 tion, into carbonic acid and water, for respiratory, motor, and calorific 

 purposes. The glycocoll, taurin, and the coloring matters are appar- 

 ently excreted. The glycocoll is probably thrown off by the kidneys 

 as urea, for when it is administered as food, more urea is then elimi- 

 nated ; the coloring matters, altered from a yellow to a greenish, and 

 then to a dark-brown hue, some taurin, and likewise a small portion of 

 the cholic acid, converted into dyalysin, are found amongst the ex- 

 creta. The excrementitious character of the bile is further indicated 

 by the size and activity of the liver before birth, when no digestion is 

 going on. Moreover, by its glycogenic function, the liver performs a 

 highly important nutritive office, affording to the body respiratory 

 food. Lastly, it may be said to act as a purifying agent on the ve- 

 nous blood returning from the alimentary canal, partly by its direct 

 power of assimilating albuminoid, oleaginous, saccharine, and coloring 

 substances, but also partly as a sort of filtering organ, in which 

 foreign bodies, such as metallic salts and other substances, are de- 

 tained, and prevented from entering too suddenly into the general 

 circulation. 



Irritation, or division, of the pneumogastric nerves, below the dia- 

 phragm, appears to produce no effect on the quantity of the bile se- 

 creted in a given time ; but injury to both, or even to one of those 

 nerves higher up, interferes with the biliary secretion, perhaps by its 

 effect on the circulation and respiration. 



When the bile is not eliminated from the system, or when it is re- 

 absorbed, symptoms of nervous prostration ensue, with headache and 

 jaundice, often followed by death. The constituents of the blood, out 



