XXVI.] 



LIVER. 



28g 



FIG. 279. Liver of Frog. C. Capillaries. 

 Osniic acid, x 300. 



of secretory activity of the cells. In some conditions the granules 

 within the cells may be arranged next the capillary ; in others they 

 are more regularly scattered throughout the cell substance. Tha 

 cells are arranged round the bile-capillaries. This is best seen in 

 transverse sections of the latter, which appear as very small circular 

 apertures bounded by four or five cells (tig. 279). When the tubes 

 are cut longitudinally, the bile 

 capillaries are seen to pursue a 

 zigzag course between the cells, 

 but this will be better seen in 

 injected specimens. 



('.) The blood-capillaries with 

 their nucleated blood-corpuscles, 

 and note that there is always a 

 cell or part of a cell between 

 the blood-stream with its wide 

 lumen, and the bile-channels 

 with very narrow lumina. Any 

 fatty granules present in the 

 osmic acid section are black. 



5. Blood- Vessels of the 



Liver Opaque Injections. Mount in balsam a section of a pig's 

 liver, with the P.V. injected with a red opaque mass, and the H.V. 

 with a similar yellow mass. The light from the reflector must be 

 turned off, and light focussed on the preparation by a condenser 

 (fig. 1 6). 



(a.) (L) Observe the polygonal lobules, the branches of the 

 portal veins around the periphery of the lobules, and sending fine 

 branches into the latter. In the centre of the lobules the hepatic 

 veinlets yellow, with capillaries converging to them. The capil- 

 laries within the lobules partly filled with red and partly with 

 yellow mass, connecting the portal and hepatic venous systems. 



(I>.) Sometimes a longitudinal section of a lobule may be seen. 

 Trace the veinlet to a larger branch under the lobule, i.e., to a 

 sublobular vein. The sublobular veinlets lie between the lobules, 

 but they differ from branches of the portal vein in not being accom- 

 panied by a branch of the hepatic artery and bile-duct. 



6. Transparent Injections Liver of Pig. Mount in the same 

 way a transparent injection of the liver of a pig. P.Y. blue, and 

 II. V. red. 



(".) (L) The hepatic veinlet in the centre of the lobule. If cut 

 transversely, it is circular ; if obliquely, oval ; and if the lobule be 

 cut longitudinally, it appears as a central channel joining a sub- 

 lobular vein. Trace outwards from this a radially-arranged capillary 

 network, with its cross-branches, right out to the outer part of each 

 26 T 



