DIGESTION. 187 



fitting closely in its cavity. Thus the bile might be either discharged 

 externally from the orifice of the canula, or allowed to pass into the 

 duodenum by its lateral opening. It was found that, after being dis- 

 charged externally for two or three hours, its rate of secretion was 

 much less than if it had been allowed to pass into the intestine. The 

 results, in a dog weighing 12 kilogrammes, were as follows: 



CUBIC CENTIMETRES OF BILE OBTAINED IN TEN MINUTES AFTER HAYING BEEN, 



FOR Two OR THREE HOURS, 



Evacuated externally. Discharged into the duodenum. 



2.2 6.0 



2.3 5.4 

 2.1 5.6 

 2.0 6.2 

 1.8 6.5 



JL9 5.7 



Average . 2.05 5.90 



Thus the quantity of bile secreted, when allowed to follow its natu- 

 ral course, is nearly three times as great as when it is evacuated exter- 

 nally. It cannot be assumed from this that the biliary ingredients are 

 returned directly to the liver, and again discharged with the bile ; but 

 it is difficult to avoid the conclusion that its ingredients are absorbed 

 from the intestine, and supply in some way the materials for continued 

 secretion. 



Finally, Tappeiner* has detected the biliary salts, by Pettenkofer's 

 test, in chyle from the thoracic duct. With 150 cubic centimetres of 

 chyle, taken from the duct two hours after feeding, in a dog weighing 

 8 kilogrammes, he obtained a complete biliary reaction by the above 

 test. 



As a rule, however, the biliary salts appear to undergo, before absorp- 

 tion, some change which modifies their original properties; and attempts 

 to distinguish them in the blood of the portal vein have constantly met 

 with a negative result. The most appropriate method for such an 

 investigation is to collect the portal blood immediately after killing the 

 animal by section of the medulla, coagulate it by the gradual addition 

 of alcohol, or by boiling with water and sodium sulphate in excess, 

 evaporate it to dryness, extract the dry residue with absolute alcohol, 

 and precipitate the filtered alcoholic solution by ether in excess. The 

 ether precipitate is then dissolved in water, and subjected to Petten- 

 kofer's test. 



We have examined the portal blood, by this method, in the dog, one, 

 four, six, nine, eleven and a half, twelve, and twenty-four hours after 

 feeding. The result shows that in the venous blood, both of the portal 

 vein and of the general circulation, there is a substance soluble in water 

 and in alcohol, and precipitable by ether from its alcoholic solution. 



* Sitzungsberichte der Akademie der Wissenschaften. Wien, 1878. Band Ixxvii. 

 Abth. in., p. 286. 



