392 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



Colin fixes the following amounts as the hourly secretion in the 

 domestic animals : — 



In the ox, 100 to 120 grammes. 



In the pig, . 75 to 160 



In the sheep, . 10 to 160 



In the dog, 8 to 15 



In the horse, . . . 250 to 300 



It would seem, therefore, that the smaller the animal the greater the 

 relative amount of bile secreted in proportion to the body weight. Thus, 

 a guinea-pig weighing one kilo, and whose liver only weighed forty 

 grammes, secreted in twenty-four hours one hundred and seventy-five 

 grammes of bile, or more than four times the weight of the liver ; and as 

 the bile of the guinea-pig contains 1 per cent, of solids, one kilo of liver- 

 substance would, in twenty-four hours, form four kilos of bile with fifty 

 grammes of solids. Since the liver onl3 r contains 25 per cent, of solids, 

 it follows that in twenty-four hours one-fifth of all the solids in the liver 

 must be eliminated in the bile. According" to Colin, the liver forms, in 

 twenty-four hours, in the horse six kilos, in the ox 2.(54 kilos, and in the 

 sheep 0.34 kilos. 



In contradistinction to the saliva, the bile is secreted under very 

 low pressure. Every slight obstruction to the flow through the duet 

 leads to reabsorption of the secretion by the hepatic lymphatic ves- 

 sels and consequent jaundice, thus showing the close connection 

 between the bile-ducts and lymphatics. This is also shown by the fact 

 that microscopic injections of the bile-ducts made after death, under 

 very low pressure, often pass into the lymphatics of the liver. While 

 the pressure under whicli the bile is secreted is comparatively low, as 

 compared with that of the saliva or that of the arterial pressure, it has 

 been stated by Heidenhain that the pressure under which the bile is 

 secreted is more than double that of the blood in the portal vein. In 

 the liver, therefore, as in the salivary glands, there can be no cpiestion as 

 to- the formation of this secretion by a mere process of filtration ; it 

 can only take place as the result of special cell activity, the specific con- 

 stituents of the bile, the bile acids and the coloring matter, being found 

 normally neither in the blood nor in any other tissue or organ, the cases 

 in whicli they or their derivatives are found elsewhere than in the bile 

 being capable of clear proof that they have only reached those localities 

 through the bile. Even after extirpation of the liver, no accumula- 

 tion of bile coloring-matter can be detected in the economy. The specific 

 constituents of the bile must, therefore, be formed in the liver-cells, and, 

 as already indicated, there is considerable proof that the coloring matter 

 originates from the breaking down of the red blood-cells, the process of 

 destruction being probably due to the action of the bile acids, heemo- 



