CHAP. XXXIII.] 



DUCT. 



469 



of capillaries. The whole of the arterial blood, therefore, which 

 supplies nutriment to the several structures of the liver, passes 



Fig. 223. 



A small lobule, showing the duct branching upon the capsule, from the pig. The saccnli of the ducta 

 are injected in this specimen. The vessel accompanying the duct is a branch of the portal vein. 



through the capillaries of the lobule before it is returned to the 

 heart, and no doubt furnishes a small portion of the matters 

 from which the bile is formed. The artery was rightly regarded by 

 Kiernan as one of the sources of the blood conveyed to the secreting 

 structure of the liver, by the branches of the portal vein. 



The gall-bladder is also supplied largely with arterial blood. 

 The arteries are arranged so as to form a beautiful network. Each 

 branch of the artery is accompanied by two branches of the vein, 

 one on either side, and when the arterial and venous networks 

 are injected with different colours a most beautiful appearance is 

 produced. A similar disposition of arteries and veins occurs in 

 the transverse fissure, and also in the large portal canals. This 

 arrangement has probably the effect of ensuring free circulation 

 through the veins in those changes of size and position to which 

 the vessels are liable. 



Duct. At least one branch of the duct accompanies each branch 

 of the portal vein, but frequently there are two or three. From 

 the branch or branches accompanying the vein, several smaller 

 ones pass off to the secreting structure. In the pig, the inter- 

 lobular ducts, while running between contiguous lobules, are 



