946 THE EXTERNAL SECRETIONS 



vena cava (Eck fistula) by uniting the edges of a longitudinal incision 

 in the wall of the former blood-vessel with those of a similar opening 

 in the latter. 1 In birds, a communication of this kind is normally 

 present in the form of a small channel which connects the capillary 

 expanse of the renal-portal system with the portal vein. Consequently, 

 the portal vein of these animals may be ligated without causing 

 serious disturbances. The total removal of the liver, however, even- 

 tually proves fatal, on account of the loss of the necessary amounts of 

 bile and other products of the hepatic cells, such as the precursors 

 of uric acid, salts and pigments. The latter are even more important 

 than the former in spite of the fact that the loss of bile gives rise to 

 serious digestive disturbances. The method of partial and total ex- 

 tirpation of the liver has been made use of more particularly as a 

 means of showing that the special constituents of the bile are actually 

 synthetized in this organ and are not brought to it in their complete 

 form. Naturally, the raw material from which these substances are 

 derived is the blood pigment, hemoglobin. This can be proved either 

 by injecting this substance into the blood stream or by inciting a greater 

 destruction of the red cells by means of hemolytic agents. It will be 

 found that the amount of the corresponding constituents of bile is 

 directly proportional to the destruction of these cells. A similar 

 reduction of the hemoglobin takes place in those tissues which have 

 been the seat of an extravasation. As the hematin of these extra- 

 vasates is slowly converted into bodies similar to the bile -pigments, 

 the tissues so affected assume different shades of purple, blue and 

 yellow. 



It has already been pointed out that the life of the red blood cor- 

 puscles is limited and that the "senile" ones are gradually removed 

 from the circulation while they traverse the capillaries of the liver and 

 spleen. But their destruction cannot be accompanied by a discharge 

 of their hemoglobin into the blood stream, because this substance is 

 taken up by the different phagocytic cells, such as the cells of Kupffer 

 lining the intrahepatic spaces. These cells also possess the power of 

 engulfing and destroying the red cells in their entirety, a process which 

 may be more directly studied in the amphibia, because the red cells 

 of these animals contain a sharply differentiated nucleus. In these 

 animals, any excessive destruction of their red cells is invariably 

 followed by an accumulation of a bright green pigment within 

 these phagocytes, which presents all the characteristics of biliverdin. 

 A similar deposition of this material takes place in the neighboring 

 endothelial lining cells as well as in the hepatic cells themselves. These 

 accumulations of pigment may be rendered more conspicuous by 

 staining them with potassium ferrocyanid which colors them blue, 



1 Nencki, Pawlow and Zaleski, Archiv fur Exp. Path., xxxvii, 1896, 26; Carrel 

 and Guthrie, Compt. rend., 1906, and Bernheim and Voegtlin, Jour, of Pharm. 

 and Exp. Ther., i, 1909, 463. 



