MECHANISM OF THE SECRETION OF BILE. 441 



was found full of bile. In addition, instances in which the portal vein emptied into 

 the vena cava have been reported, and in none was there any deficiency in the secretion 

 of bile. 



If the experiments upon the effects of tying the hepatic artery, and the observations 

 of instances of obliteration of the portal vein and of congenital malformation, in which 

 the portal vein does not go to the liver, be equally reliable, there is but one conclusion 

 to be drawn from them ; and that is, that bile may be secreted from either venous or 

 arterial blood. This view is not inconsistent with what we know of the general process 

 of secretion and its applications to the production of bile. Regarding the bile as in part 

 an excrementitious fluid, its effete element, cholesterine, is contained both in the blood 

 of the portal vein and the hepatic artery. Its recrementitious principles, glycocho- 

 lates, taurocholates, etc., we suppose are produced de novo in the liver, out of materials 

 furnished by the blood. The exact nature of the production of elements of secretion by 

 glandular cells we do not understand ; but there is no good reason to suppose that the 

 principles necessary for the formation of bile may not be furnished by the blood of the 

 portal vein, as well as by the hepatic artery. 



The view most nearly in accordance with all the facts bearing on the question is, that 

 bile is produced in the liver from the blood distributed in its substance by the portal vein 

 and the hepatic artery, and not from either of these vessels exclusively ; and that the bile 

 may continue to be secreted, if either one of these vessels be obliterated, provided the 

 supply of blood be sufficient. 



Quantity of Bile. The estimates of the daily quantity of bile in the human subject 

 must be merely approximative ; and our only ideas on this point are derived from experi- 

 ments upon the inferior animals. The most complete and reliable observations upon this 

 subject are those of Bidder and Schmidt, which were made upon animals with a fistula into 

 the gall-bladder, the ductus communis having been tied. These observers found great 

 variations in the daily quantity in different classes of animals, the quantity in the car- 

 nivora being the smallest. Applying their results to the human subject, assuming that 

 the amount is about equal to the quantity secreted by the carnivora, the daily secretion 

 in a man weighing one hundred and forty pounds would be about two and a half pounds. 



Variations in the Flow of the Bile. We have already considered, under the head of 

 digestion, the variations in the flow of bile and their relation to the process of intestinal 

 digestion. It is sufficient in this connection to repeat that the discharge from a biliary fis- 

 tula in a dog increases immediately after eating ; that it is at its maximum from the second 

 to the eighth hour, during which time it does not vary to any great extent ; after the eighth 

 hour it begins to diminish ; and, from the twelfth hour to the time of feeding, it is at it& 

 minimum. These facts show that, while the bile is discharged much more abundantly 

 during intestinal digestion than during the intervals of digestion, its production and dis- 

 charge are constant. This, as we shall see farther on, is a strong argument in favor of 

 the view that the liver has an excrementitious function. 



The bile is stored up in the gall-bladder to a considerable extent during the intervals 

 of digestion. If an animal be killed at this time, the gall-bladder is always distended ; 

 but it is found empty, or nearly so, in animals killed during digestion. 



The influence of the nervous- system upon the secretion of bile has been very little 

 studied, and the question is one of great difficulty and obscurity. The liver is supplied 

 very abundantly with nerves, both from the cerebro- spinal and the sympathetic system, 

 and some observations have been made upon the influence of the nerves upon its glycogenic 

 function ; but, with regard to the secretion of bile, we can only apply our general remarks 

 concerning the influence of the nervous system on secretion. 



The bile is discharged through the hepatic ducts like the secretion of any other gland. 

 During digestion, the fluid accumulated in the gall-bladder passes into the ductus com- 



