THE MICROSCOPE IN ANIMAL HISTOLOGY. 211 



forms the radicle of the hepatic vein ; while externally 

 the lobules are bounded by branches of the portal vein 

 and biliary canals (Plate XXIII, Fig. 169). The hepatic 

 artery nourishes the proper connective tissue of the organ, 

 and its venous radicles return the blood to the portal 

 vein. The liver or bile-cells lie between the meshes of 

 the capillaries, and are irregularly polyhedral from pres- 

 sure, soft, granular, and nucleated. Brown pigment-gran- 

 ules and fatty globules are also found in the cells, and in 

 disease in increased quantity. These bile-cells are inclosed 

 in a delicate reticulated membrane, and Hering considers 

 them to have a plexus of fine bile-ducts around them. 



The kidneys are two large bean-shaped organs, each 

 covered with a thin but strong fibrous envelope or tunic, 

 which is continuous round the organ to the hilus, where 

 the ureter leaves the gland and the bloodvessels enter. 

 Even with the naked eye we may distinguish in a section 

 of kidney the external granular cortex and the fibrous or 

 striped medullary portion. The lines of the latter con- 

 verge towards the hilus, and generally in a single conoid 

 mass ; but in man and some other animals this is divided 

 into sections, called the pyramids, and between them the 

 cortical substance is prolonged in the form of septse, while 

 both portions contain interstitial connective tissue. Both 

 the cortical and medullary portions contain long branch- 

 ing glandular tubes, called the uriniferous tubes. In the 

 medullary part these tubes are straight and divide at 

 acute angles, while in the cortex they are greatly convo- 

 luted and terminate in blind dilatations, the capsules of 

 Bowman. Staining with nitrate of silver shows the cap- 

 sules to be lined with delicate pavement-epithelium. The 

 convoluted tubes proceeding from the capsules, containing 

 thick granular gland-cells, after numerous windings in the 

 cortex, arrive at the medullary portion, where each pur- 

 sues a straight course, and is lined with flat pavement- 

 epithelium similar to the endothelium of vascular tissue. 



