188 



THE DIGESTIVE SYSTEM 



lobular ^'ein which e\'entiially unites with the hepatic ^•eins, the 

 efferent blood vessels of the liver. In addition to the endothelial 

 cell proper, which is small and flat with a darkly staining nucleus, 

 there are present along the walls of the sinusoids other larger cells, 

 the Kupffer cells. Kupffer cells have a number of cytoplasmic 

 processes and a larger vesicular nucleus. By intravenous injection 

 the Kupfl'er cells can be shown to be active in ingesting foreign 

 particles from the blood passing through the sinusoids, i. e., they 

 become macrophages. They may be considered as homologous with 

 histiocyte cells and are part of the reticulo-endothelial system. 

 Some believe thev are derived from the cells of the delicate reticular 



Fig. 122.— Photograph of injected bile capillaries in the liver of a rabbit. These 

 are indicated by the network in black. Nuclei of liver cells are faintly stained and the 

 cord-like arrangement of liver cells is evident. 



tissue enveloi)ing the sinusoids; others consider them derived from 

 endothelial cells. Possibly both sources are correct. 



Histiocytes or reticulocytes and endothelial cells, forming the sin- 

 usoids in the spleen and marrow, and Kupffer cells are considered 

 homologous and constitute the reticulo-endothelial system, im- 

 portant physiologically because of its phagocytic potentialities. 



Between the adjacent faces of the hei)atic cells the l)ile cai)illaries 

 appear as grooves between the adjoining cell walls. By silver 

 impregnation and injection the bile capillaries (Fig. 122) appear to 

 be bounded by a delicate non-cellular membrane formed by the 

 adjoining hepatic cell walls. These ca])illaries are functionally 

 comparable to the lumens of other glands, and into them is collected 



