8UGAES. 59 



articles of food, in the blood of the portal vein. It is not 

 found in other organs, nor does it normally exist in the 

 arterial blood. 



During the first three or four months of foetal life sugar 

 is formed by the placenta, and exists in all the fluids of the 

 foetus, in greater quantity even than after birth. At the 

 third or fourth month the liver begins to take on this func- 

 tion, which is gradually lost by the placenta. The constant 

 production of this principle in the economy, even in the 

 early months of fcetal life, is significant of the importance of 

 its function. 



The function of sugar and its mode of disappearance in 

 the economy are not yet well understood. Its early forma- 

 tion in large quantity, when the processes of nutrition are 

 most active, seems to point to an important office in the 

 performance of this general function. Its presence is un- 

 doubtedly necessary at all periods of life ; for its formation 

 never ceases in health. Bernard has attempted to show that 

 its presence in the animal fluids favors cell development, but 

 has hardly succeeded in establishing this fully. 1 



It has been claimed that the sugars and fats are for the 

 purpose of keeping up the animal temperature, and are 

 oxidized or undergo combustion in the lungs. This view 

 was afterwards modified by Liebig and others, who supposed 

 that the oxidation takes place in the general system. This 

 theory will be discussed more fully in the chapter on animal 

 heat. Here we can only say that, while there are many cir- 

 cumstances which, taken by themselves, might lead to such 

 a conclusion, the production of heat in the body is closely 

 connected with the general process of nutrition, of which the 

 disappearance of oxygen and formation of carbonic acid are 

 but a single one of many important changes. "We have not yet 

 sufficient ground for the supposition that the substances under 

 consideration are directly and exclusively acted upon by oxy- 



1 BERNARD, Lemons de Physiologic Experimental, Paris, 1855, p. 247 et seq. 



