CHAP. IV.] BLOOD-PRESSURE AND BILE SECRETION. 



285 



Changes in 

 pressure in the 

 portal system 

 and their in- 



operation recovered from its immediate effects. A series of nervous 

 symptoms manifested themselves which were unquestionably due to a 

 constituent (carbamic acid) of the portal blood which is normally 

 arrested and transformed by the liver, finding its way into the general 

 circulation. There was no evidence, however, of an arrest of the flow 

 of bile, during the .time when the portal blood was cut off, and before 

 a collateral circulation of portal blood to the liver was established \ 



The conclusion which, it appears to the Author, can be legiti- 

 mately deduced from the facts cited is, that in cases of occlusion of the 

 portal vein, the hepatic artery is able to supply the liver with sufficient 

 blood to permit of its usual operations being performed, though in an 

 impaired manner, and consequently the secretion of bile (which is not a 

 function per se, but rather a resultant of all the chemical processes of 

 the organ) is not arrested. It must not be forgotten, however, that 

 in these exceptional cases the hepatic artery carries to the liver 

 blood which differs greatly from that which it usually conveys, inas- 

 much as the blood of the general circulation contains an unusual 

 proportion of materials which have more or less directly reached it 

 from the portal area. 



' The supply of blood for the liver is mainly that 

 through the vena portas ; and this supply is not, like 

 _ an arterial supply, a fairly uniform one, modified chiefly 

 fluence on the by the vaso-motor wants of the organ itself, but is de- 

 flow of one. pendent on what happens to be taking place in the 

 alimentary canal and abdominal organs other than the liver itself. 



' When no food is being digested and the alimentary canal is 

 at rest, the vessels of that canal are, like those of the stomach, pan- 

 creas and salivary glands, in a state of tonic constriction ; a relatively 

 small quantity of blood passes through them ; hence the flow through 

 the vena portse is relatively inconsiderable ; and the pressure in that 

 vessel is low. When digestion is going on all the minute arteries of 

 the stomach, intestines, spleen and pancreas are dilated, and general 

 exterior pressure being by some means or other maintained, a rela- 

 tively large quantity of blood rushes into the vena portse and the 

 pressure in that vessel becomes much increased, though of course 

 necessarily lower than the general arterial pressure. Moreover 

 during digestion, peristaltic movements of the muscular coats of the 

 alimentary canal are active ; and these movements, serving as aids 

 to the circulation, help to increase the portal flow. Further, the 

 spleen is in many animals richly provided with plain muscular fibres, 

 and in these cases seems, especially during digestion, to act as a 

 muscular pump driving the blood onwards, with increased vigour, 

 along the splenic veins to the liver. So that even were the liver not 

 connected with the central nervous system by a single nervous tie, 



1 'La Fistule d'Eck de la veine cave inferieure et de la veine porte et ses cons6- 

 quences pour Forganisme. Par MM. les Drs M. Halm, V. Massen, M. Nencki et 

 J. Pawlow. (Travail des laboratoires de M. Nencki et de M. Pawlow.)' Archives dcs 

 Sciences Bioloqiques publiees par VInstitut Imperial de Medecine Experimentale a 

 St. -Petersburg. Tome i. (1892), no. 4, pp. 401495. 



