Chap, hi.] THE TRANSFOEMATION OF FORCES IN BIOLOGY. 461 



bodies. But, in the animal macliine, the most important chemical 

 acts are osydations, combnstions. The alimentary matters intro- 

 duced into an animal organism represent molecular systems 

 containing forces of tension, that is to say, groups of molecules, in 

 which the atomic attractions mutually balance each other. Once 

 transfused in the nutritive vertex, from contact with the aerial 

 oxygen, these bodies oxydate, their molecular equilibrium is 

 destroyed ; they then set at libei'ty vival forces, that is to say, 

 that the molecular attractions no longer neutralise each other ; the 

 atomic movements may be communicated to the ambient medium, 

 and consequently be transformed into heat, into electricity, into 

 movement, mechanical, or of totality.^ In fact these are the 

 three principal methods of transformation of the molecular move- 

 ments in the essence of the animal tissues. We know that in 

 the nervous and muscular fibres there is an electric current from 

 the surface to the centre, and this current results directly from 

 oxydation ; for it is still more clearly produced, as M. Becquerel 

 has proved, in muscular tissue when mangled, which then oxy- 

 dateSjOr rather respires, more energetically than in its normal state. 

 We have pointed out, in their place and order, the electric phenomena 

 which take place in the capillary vessels. Analogous electric 

 currents are probably developed in all the living tissues. 



It is much easier to prove organic heat than electricity. It is, 

 moreover, the form which the greater part of the vival forces of 

 the free molecular movements takes in the animal machine. We 

 have seen that this heat maintained the bodies of the higher 

 vertebrates at a temperature of from 36 to 40 degrees. 



Ingenious experiments have proved that muscular movements 

 as well as organic heat have their source in the chemical com- 

 binations of the animal machine. It has been observed that 

 muscular activity corresponded to an augmentation of the con- 



^ In biology, the expression vival forces must be taken simply in a meta- 

 phorical sense, in the sense of free forces, of Ivvmg forces, as Helmholtz calls 

 them {Zebendige Krdfte). Biological meohanik is not yet sufficiently ad- 

 vanced for us to give to the expression vival force the value wlfich it has in 

 mechanik, that of the product of the mass by the square of the velocity. 



