356 A MANUAL OF PHYSIOLOGY 



the whole intestinal tract out of gear. But after an artificial com- 

 munication has been made between the portal and the left renal 

 vein or the inferior cava, the portal may be tied and the 

 animal live for months (Eck). The liver can now be completely 

 removed, but death follows in a few hours. A good method of 

 establishing an Eck's fistula is to make a longitudinal incision 

 in the inferior vena cava and the portal or superior mesenteric 

 vein, and to suture the edges of the two openings together with a 

 very fine sewing-needle and thread (Carrel and Guthrie).* In 

 birds there exists a communicating branch between the portal 

 vein and a vein (the renal-portal) which passes from the posterior 

 portion of the body to the kidney, and there breaks up into 

 capillaries ; and not only may the portal be tied, but the liver 

 may be completely destroyed without immediately killing the 

 animal. In the hours of life that still remain to it no accumula- 

 tion of biliary substances takes place in the blood or tissues. A 

 further indication that bile-pigment is produced in the liver is the 

 fact that the liver contains iron in relative 

 abundance in its cells (p. 21), and eliminates 

 small quantities of iron in its secretion. 

 Now, bile-pigment, which contains no iron, is 

 certainly formed from blood-pigment, which 

 is rich in iron, for hsematoidin (Fig. 142), a 

 crystalline derivative of haemoglobin found 

 in old extravasations of blood, especially in 

 the brain and in the corpus luteum, is identi- 



FlG. 142. H^EMATOIDIN. , .,, v-i t. ' T^1_ X ' j.' X 



cal with biJirubin. I he seat ol formation oi 

 bile-pigment must therefore be an organ peculiarly rich in iron. 

 The existence of haematoidin, however, shows that bile-pigment 

 may, under certain conditions, be formed outside of the hepatic 

 cells. The occurrence of biliverdin in the placenta of the bitch 

 points in the same direction. But the pathological evidence in 

 favour of the pre-formation of the biliary constituents tends 

 rather to shrink than to increase. For many cases of what used 

 to be considered ' idiopathic ' or ' haematogenic ' jaundice, 

 i.e., an accumulation of bile-pigments and bile-acids in the 

 tissues, due to defective elimination by the liver, are now known 

 to be caused by obstruction of the. bile-ducts and consequent re- 

 absorption of bile (' obstructive ' or ' hepatogenic ' jaundice). 



But if substances such as the ferments, mucin, hydrochloric 

 acid, the bile-salts and bile-pigments, are undoubtedly manu- 

 factured in the gland-cells, it is different with the water and 

 inorganic salts which form so large a part of every secretion. 



* By means of a small clamp, the jaws of which are shaped so as to 

 isolate a longitudinal strip at one side of a bloodvessel while the circulation 

 goes on through the rest of the lumen-, the veins may be opened and 

 sutured without interrupting the circulation. 



