240 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



quoted in the section on Digestion (p. 322), 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-duet 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 t<> the animal's lite, we possess numerous statistics as tothedailv quantity 

 of the secretion formed. Surgical operations upon human beings (see p. 321 

 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 500 

 to 800 euliie 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. 



Eatio 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 4.0(54 : 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 

 with a biliary fistula showed that the secretion was ejected in spirts, owing 

 doubtless to contraction- of the muscular walls of the larger bile-ducts. But 

 though continuously formed within the liver-cells, the flow of bile is subject 

 to considerable variations. According to most observers the activity of secre- 

 tion is definitely connected with the period of digestion. Somewhere from the 

 third to the fifth hour after the beginning of digestion there is a very marked 

 acceleration of the flow, and a second maximum at a later period, ninth to 

 tenth hour (Hoppe-Seyler), has been observed in dogs. The mechanism con- 

 trolling the accelerated How during the third to the fifth hour is not perfectly 

 understood. It would seem to be correlated with the digestive changes occur- 

 ring in the intestine, but whether the relationship is of the nature of a reflex 

 nervous act, or whether it depends on increased blood-flow through the organ 

 or upon some action of the absorbed products of secretion remains to be deter- 

 mined. It has been shown that the presence of bile in the blood acts as a 

 stimulus to the liver-cells, and it is highly probable that the absorption of bile 

 from the intestine which occurs during digestion serves to accelerate the secre- 

 tion ; but this circumstance obviously does not account for the marked increase 

 observed in animals with biliary fistulas, since in these cases the bile does not 

 reach the intestine at all. Therapeutically various substances have been 

 stated by different authors to act as true cholagogues — that is, to stimulate the 

 1 Hermann's Handbuch der Physiologic, Bd. v. Thl. I, S. 253. 



