186 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



most carnivorous animals it is golden red, while in the herbivora it is green, 

 the difference depending on the character and quantity of the pigments. In 

 man the bile is usually stated to follow the carnivorous type, showing a red- 

 dish or brownish color, although in some cases apparently the green predomi- 

 nates. The characteristic constituents of the bile are the pigments, bilirubin in 

 carnivorous bile and biliverdin in herbivorous bile, and the bile acids or bile- 

 salts, the sodium salts of glycocholic or taurocholic acid, the relative proportions 

 of the two acids varying in different animals. In addition there is present a 

 considerable quantity of a mucoid nucleo-albumin, a constituent which is not 

 formed in the liver-cells, but is added to the secretion by the mucous membrane 

 of the bile-ducts and gall-bladder ; and small quantities of cholesterin, lecithin, 

 fats, and soaps. The inorganic constituents comprise the usual salts chlorides, 

 phosphates, carbonates and sulphates of the alkalies or alkaline earths. Iron 

 is found in small quantities, combined probably as a phosphate. The secre- 

 tion contains also a considerable though variable quantity of CO 2 gas, held in 

 such loose combination that it can be extracted with the gas-pump without the 

 addition of acid. The presence of this constituent serves as an indication of 

 the extensive metabolic changes occurring in the liver-cells. Quantitative 

 analyses of the bile show that it varies greatly in composition even in the same 

 species of animal. Examples of this variability are given in the analyses 

 quoted in the section on Digestion (p. 261), where a brief account will also be 

 found of the origin and physiological significance of the different constituents. 

 The Quantity of Bile Secreted. Owing to the fact that a fistula of the 

 common bile-duct or gall-bladder may be established upon the living animal 

 and the entire quantity of bile be drained to the exterior without serious detri- 

 ment to the animal's life, we possess numerous statistics as to the daily quantity 

 of the secretion formed. Surgical operations upon human beings (see p. 261 

 for references), made necessary by occlusion of the bile-passages, have furnished 

 similar data for man. In round numbers the quantity in man varies from 600 

 to 800 cubic centimeters per day, or, taking into account the weight of the 

 individuals concerned, about 8 to 16 cubic centimeters for each kilogram of 

 body-weight. Observations upon the lower animals indicate that the secretion 

 is proportionally greater in smaller animals. This fact is clearly shown in the 

 following table, compiled by Heidenhain * for three herbivorous animals : 



Sheep. Rabbit. Guinea-pig. 



Ratio of bile-weight for 24 hours to body-weight . . . 1 : 37.5 1 : 8.2 1 : 5.6 



Ratio of bile-weight for 24 hours to liver-weight . .- . 1.507 : 1 4.064 : 1 4.467 : 1 



There seems to be no doubt that the bile is a continuous secretion, although 

 in animals possessing a gall-bladder the secretion may be stored in this reser- 

 voir and ejected into the duodenum only at certain intervals connected with 

 the processes of digestion. The movement of the bile-stream within the 

 system of bile-ducts that is, its actual ejection from the liver, is also probably 

 intermittent. The observations of Copeman and Winston on a human patient 

 1 Hermann's Handbuch der Physiologic, vol. v. Thl. 1, p. 253. 



