324 ANIMAL PHYSIOLOGY. 
increase in the quantity of bile secreted, followed by a sudden 
diminution, then a more gradual rise, with a subsequent fall. 
Almost the same holds for the pancreas. 
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23[1| 2[ 3] 4] 5] 6|7 [8] 9]10/11]12)13]14]15]16] 1] 2] 3] 4] 5] 6/7] 8/9 {10 
Fie. 274.—Diagram to show influence of food in secretion of pancreatic juice (after N. O. Bern- 
stein). The abscissze represent hours after taking food ; ordinates amount in cubic centi- 
grammes of secretion in ten minutes. Food was taken at B and C. This diagram very 
nearly also represents the secretion of bile. 
It seems impossible to explain these facts, especially the 
first rapid discharge of fluid apart from the direct influence of 
the nervous system. 
Upon the whole, the evidence seems to show that the press- 
ure in the bile-ducts is greater than in the veins that unite to 
make up the portal system; but there are difficulties in the 
investigation of such and kindred subjects as regards the liver, 
owing to its peculiar vascular supply. It will be borne in mind 
that the liver in mammals consists of a mass of blood-vessels, 
between the meshes of which are packed innumerable cells, and 
that around the latter meander the bile capillaries; that the 
portal vein breaks up into the interlobular, from which capil- 
laries arise, that terminate in the central intralobular veins, 
which make up the hepatic veinlets or terminate in these vessels 
But the structure is complicated by the branches of the hepatic 
artery, which, as arterioles and capillaries, enters to some extent 
into the formation of the lobular vessels. It is remarkable that 
the cells of the liver are so similar, considering the complicated 
functions they appear to discharge. 
