PUTREFACTION IN BLOOD. 51 



sistance of the air in order to continue putrefaction ; and in 

 nature it is generally found that putrefaction takes place 

 in a very imperfect supply of air, in cases which in reality 

 greatly resemble a closed vessel : the surface is generally 

 exposed, but all below receives a very imperfect supply of 

 air. In a similar way, the vessel was occasionally allowed 

 air, whilst generally it was closed — ^the constant very slow 

 supply in nature being equal to the occasional replenish- 

 ing here adopted. 



The amount of gas obtained by this method was not 

 quite so large as I expected. It was needful to raise the 

 temperature above that of the atmosphere during a large 

 portion of the year. It seemed to me as if 54° Fahr. 

 were a point to be marked especially. Below this there 

 was little decomposition, above this a decidedly larger 

 amount. However, the evolution of gas did not entirely 

 cease when the temperature fell below 54°, neither did the 

 increase arrive at its maximum on passing 54°. When the 

 temperature rose towards 70°, the escape of gas was much 

 more abundant ; but this was rare, as the vessels were kept 

 in an apartment not readily warmed, and they were too 

 large to be moved frequently with safety. 55° Fahr. is 

 generally marked temperate on our thermometers, and the 

 characteristic of organic matter to be more active at this 

 temperature is remarkable. The mere feeling of warmth 

 and cold had long ago fixed on this point as marking the 

 beginning of activity or inactivity in the materials of which 

 we are composed. The feeling of cold arises no doubt from 

 slowness in the decomposition of certain substances in the 

 blood, and slowness of oxidation. 



The relative amount of gas given off at different tem- 

 peratures seemed to me a mode of measuring the relation 

 of climates as far as danger from putrid substances is con- 

 cerned, possibly also the production of disease. I have not 

 obtained the amount of gas given off below 54° -Fahr. ; but 



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