THE DIGESTION 



229 



FIG. 181. Diagram to show the Termination of a 

 Fine Bile Duct. 



b, small bile duct becoming still finer at b' ; /, hepatic cells; 

 c, capillaries cut across. 



rabbits be well fed and one kept in a cage and the other 



hunted around all day, much glycogen will be found in 



the liver of the quiet rabbit, and very little in the liver 



of the hunted one. 



The glycogen stored 



up is used during 



muscular work or 



starvation. 



406. The sugar 



absorbed by the 



small intestine 



reaches the liver 



through the portal 



vein. It is taken 



up by the liver cells 



and changed into 



granules of glyco- 

 gen, to be turned 



into sugar again during times of hunger and hard work. 



Thus only a small amount of sugar is allowed to enter 



the circulation at one time, only ij ounces in every 



1000 ounces of arterial 

 blood. If more than this 

 quantity enters the blood, 

 sugar passes out through 

 the kidneys, and the func- 

 tion of the kidneys may be- 

 come disordered, a condi- 

 diabetes." 



Urea is the chief 

 waste product which results 



from the breaking down of proteid, and it is believed that 

 the nitrogenous urea as well as the carbohydrate glycogen 

 is formed by the liver. An excess of proteid, such as 

 lean meat and cheese, in the diet, produces an increased 



FIG. 182. Liver Cells of Dog after a Thirty- 

 six Hours' Fast ; also Fourteen Hours after tion known as 



