IDENTICAL WITH THEIR BODIES. 57 



metamorphosed into new combinations, which are 

 amorphous and unorganised. 



The food of the carnivora is at once converted 

 into blood ; out of the newly-formed blood those 

 parts of organs which have undergone metamor- 

 phoses are reproduced. The carbon and nitrogen of 

 the food thus become constituent parts of organs. 



Exactly as much carbon and nitrogen is supplied 

 to the organs by the blood, that is, ultimately, by 

 the food, as they have lost by the transformations 

 attending the exercise of their functions. 



What then, it may be asked, becomes of the new 

 compounds produced by the transformations of the 

 organs, of the muscles, of the membranes and cel- 

 lular tissue of the nerves and brain ? 



These new compounds cannot, owing to their 

 solubility, remain in the situation where they are 

 formed, for a well-known force, namely the circu- 

 lation of the blood, opposes itself to this. 



By the expansion of the heart, an organ in which 

 two systems of tubes meet, which are ramified in a 

 most minute network of vessels through all j^arts of 

 the body, there is produced a vacuum, the imme- 

 diate effect of which is, that all fluids which can 

 penetrate into these vessels are urged with great 

 force towards one side of the heart by the external 

 pressure of the atmosphere. This motion is power- 

 fully assisted by the contraction of the heart, alter- 

 nating with its expansion, and caused by a force 

 independent of the atmospheric pressure. 



