20 ANIMAL MECHANISM. 



connected with influences of nervous origin, when it was 

 seen that certain violent emotions produce icy coldness in 

 human. beings, whereas others bring into the countenance 

 sudden heat. Now all these facts have found an explanation 

 in which there is nothing to infringe the ordinary laws of 

 physics. In order to comprehend them thoroughly we must 

 pass under our review the production of heat and its dis- 

 tribution throughout the various parts of the organism. 



It has long since been established that aliment is indis- 

 pensable in the living being for the production of heat, as well 

 as of muscular power. Inanition, at the same time that it 

 reduces the strength of the animal, produces profound cold 

 in it. We owe to the genius of Lavoisier the comparison 

 of the living organism to a grate which burns or incessantly 

 oxidizes substances taken from without, by borrowing from 

 the atmosphere the oxygen requisite for these transforma- 

 tions. This theory has triumphed over all the attacks which 

 have been made upon it, and their only result has been the 

 perfecting of its details. 



Let us reduce to its true proportions the comparison of the 

 living organism with a burning grate. In both, an oxidable 

 matter finds itself placed in relation with oxygen ; but while, 

 in a grate, the natural gas comes in contact with the com- 

 bustible previously raised to an elevated temperature, in the 

 organism the gas dissolved in the blood comes in contact with 

 materials which are themselves dissolved in that liquid, or 

 which have deeply entered into the tissue of the organs. 

 Thus, the circulation transports into every part of the 

 organism the elements which are necessary to the disengage- 

 ment of force. These bodies remain in contact, without acting 

 one upon the other, until the moment arrives when a specific 

 action brings about their combination. This oilice, analogous 

 to that of the spark which kindles the- Hume, or to that of 

 the cap which discharges gunpowder, belongs to the nervous 

 system. 



When tin- oxidation is at an end, and the forces necessary 

 to the functions have been s< t at liberty, there remain in the 

 tissues certain products which have become useless, and which 

 may be compared to the ashes in the grate and to the gases 



