84 THE HUMAN BODY. 



which secrete or transport the fluids extracted from the blood 

 by the liver to the gall-bladder, situated under the right lobe. 



The tissue proper of the liver is essentially constituted by 

 the secretory canals of the bile, each one of which ter- 

 minates in an acinus or lobule ; a net-work of capillaries of 

 the portal vein surrounds these lobules, which by their union 

 in clusters form the liver, and which are so many diminu- 

 tives of that gland. The secretory ducts are continuous 

 with the hepatic ducts, and the capillaries of the portal vein 

 with those of the hepatic veins, which transmit to the inferior 

 vena cava the blood from which the bile has been separated. 

 The liver secretes sugar also, which, formed in this gland at 

 the expense of the blood from the portal vein, is immediately 

 decomposed, and in health disappears in the process of 

 nutrition. 



Pancreas. This is an elongated gland situated behind the 

 stomach : it secretes the pancreatic juice a fluid analogous 

 to the saliva, and which the pancreatic canal pours into the 

 ductus choledochus, near its orifice in the duodenum. 



Spleen. This is a spongy vascular body situated in the 

 left hypochonder, between the stomach and the false ribs: 

 it serves as a reservoir in over-fulness of the portal vein. Its 

 special use and purpose are unknown. 



The kidneys are two in number, and are placed on the 

 right and left of the lumbar vertebrae in the lowest part of 

 the hypochonders. They are glands of a peculiar and very 

 complicated structure. They separate the urea from the 

 blood, and transmit to the bladder the urinary secretion by 

 two canals called ureters. The upper portion of the kidneys 

 is covered by the supra-renal capsules, the use of which is 

 not known. 



Mechanism of digestion. This function consists in the 

 decomposition, liquefaction, and absorption of alimentary 

 substances; it prepares the nutriment by separating the 

 assimilable portions which are to be mingled with the blood 

 from those which are not fit to enter into the organism. 

 The aliments undergo in the mouth the first change neces- 

 sary to their introduction into the digestive canal, which is 

 also no less important in relation to their chemical trans- 



