KATABOLISM. ,,, 



But there are several others — viz., the thymus, the thy- 

 roid, the suprarenal, etc. Their functions are very ob- 

 scure, but very important. Only recently has attention 

 been strongly drawn to them. Their products have been 

 called internal secretions. 



Again, the ducted glands, as already explained, are of 

 two kinds — secretory and excretory. The one manu- 

 factures useful products out of the blood, the other 

 eliminates hurtful products of katabolism from the 

 blood. 



Now, the liver belongs to all three kinds. It manu- 

 factures two things— viz., bile and sugar. As a ducted 

 gland it delivers its bile by a duct into the intestines. 

 As a ductless gland it delivers its sugar directly to the 

 blood. Again, the bile is both a secretion used in the 

 digestive process and an excretion, purifying the blood 

 of the hurtful katabolic products. 



Therefore the function of the liver is threefold: (i) 

 The manufacture of sugar, (2) the manufacture of bile 

 as a secretion, and (3) the elimination of bile as an excre- 

 tion. This last is probably connected with the destruc- 

 tion of the red blood-globules in the liver. We have 

 already discussed the bile as a digestive secretion. We 

 have also already spoken of the liver as the cemetery of 

 red globules, and said all that was necessary in the very 

 imperfect state of knowledge on this subject. All that 

 remains is the discussion of the liver as a manufactory of 

 sugar. This introduces the very important subject of 

 glycogen}-. 



Glycogeny and its Relation to Vital Force and 

 Vital Heat. — If we examine the blood of the hepatic 

 vein we always find a notable quantity of sugar. 

 Whence comes it ? It is at first natural to suppose that 

 it comes from the digested food, the sugar of which, we 

 have already seen, is taken up by the capillaries of the 



