130 BIOLOGY. [Book ir. 



exchanges of material which are the very foundation of nutrition. 

 CI. Bernard has proved that a portion of these ternary compounds 

 form themselves direct, by synthesis, in animal tissues as well as 

 in those of plants. The liver of animals forms in its cells 

 an amyloidal matter denominated glyeogene, which is afterwards 

 transformed into sugar. The placenta of the larger number of 

 mammifers is also a producer of glyeogene. The placenta of 

 ruminants seems to form an exception, but the glycogenical 

 function is then fulfilled by platings, by special villosjties of 

 the amnios. We also find sugar in the muscles of the foetus, 

 in the larger portion of the epithelial cells covering its mucous 

 membranes, in the bones and the cai-tilages. In the crab, where 

 development is achieved by sudden bounds, by moultings, the 

 liver only contains glycogenical matter during these periods of 

 rapid growth. 



It seems certain that the glycogenical cells of the liver, and 

 all the analogous cells, can synthetically form glycogenical matter 

 at the expense of the aliments, whatever they may be ; but it 

 seems also incontestable that they directly utilize substances of 

 a similar composition contained in the aliments. M. "W. Pavey 

 has, in effect, shown that in dogs fed exclusively upon animal 

 aliment, the mean proportion of glycogenical matter was 6 '97 in 

 the 100, whilst it rose to 17'23 per 100 in dogs fed upon boiled 

 potatoes, barley-meal, and bread. Finally, the proportion was 

 14"5 in the 100 when a considerable portion of sugar was added 

 to the ration of animal food.^ 



We have said that the combustion of hydro-carbonized matters 

 in the organisms developed heat, which was afterwards utilized 

 in the reactions of living chemistry. We shall see farther on 

 that a portion of this heat can also transform itself dii-ect into 

 muscular movementSi In effect, we find sugar in the muscles of 

 the foetus, in the tissue of muscles immobilized by the section 

 of their motory nerves, and in the muscles of animals in the 



' The Influence of the Diet on the Liver. London. ijSfuy's ffospital Bepm'ts, 

 1859.) 



