134 



PHYSIOLOGY 



CHAP. 



The interlobular course of the hepatic duct is similar to that 

 of the portal vein and the hepatic artery, but its interlobular 

 branches form a much finer network of canaliculi than that 

 formed by the blood-vessels, as shown in Fig. 48. 



The hepatic cells lie in the interstices of the network of blood 

 capillaries, and round the closer meshes of the bile canaliculi. 

 They are polyhedral, 17-22 /j. in diameter, destitute of cell 

 membrane, and have a clear nucleus, with intranuclear network, 

 and one or two nucleoli. 



The finely reticulated cytoplasm, the deutoplasmic content, 



and the aspect as a whole of 

 the liver-cells change consider- 

 ably (as we shall see below) 

 according to whether they are 

 examined in the fasting state 

 or after food. Fig. 49 shows 

 the relations and respective size 

 and position of the hepatic cells, 

 the network of blood capillaries, 

 and the finer network of bile 

 canaliculi. 



The nerves to the liver are 

 branches of the vagus and of 

 the solar plexus of the sym- 

 pathetic. They enter by the 

 portal fissure, accompanying the 

 hepatic artery and the portal 

 vein. They consist partly of 

 medullated, partly of non-medul- 

 lated fibres. The latter are dis- 



FIQ. 49. Section of rabbit's liver after injection tl'ibllted almost exclusively to 

 of intracellular network of bile capillaries. , , . 1,1 , , 



(Herin-.) Thick section, showing two or the arteries and the veins ; the 



three layers of cells and relative size and f nrmpr p n rp r flip lnlmlp<3 whprp 

 position of blood capillaries, b, b ; bile canali- les > W11616 



cuii, c, c ; and hepatic ceils, e, e. they i ose their medullary sheaths 



and ramify between and over 

 the cells, in a network of fine filaments (Fig. 50). 



XIX. The external secretion of Bile produced by the liver 

 is distinguished from the four secretions above described, by 

 being continuous although it presents considerable fluctuations, 

 particularly in relation to the state of digestion or fasting; by 

 having no specific enzymes; and by being apparently regulated 

 merely by the hydraulic conditions of the hepatic circulation and 

 absorbed digestive products, independent of any direct influence 

 of secretory nerves, to which the other digestive secretions proper 

 are subordinated. For all these reasons the biliary secretion 

 presents more analogy with the secretion of urine as performed by 

 the kidneys than with the secretions of digestive juice which we 



