HEAT AND LIFE. 149 



sations of life in all beings become more rapid ; but this 

 stimulus is only fleeting, and soon, when it reaches a cer- 

 tain degree, this heat gives place to the cold of death. 

 Bernard carefully examined animals dying under these con- 

 ditions, and the first phenomenon that struck him was the 

 rapidity with which corpse-like rigidity came on. The 

 heart grew suddenly insensible to any stimulus ; effused 

 spots appeared at several points on the skin. The heat 

 fixed in coa.gulation the soft matter that composes the mus- 

 cular fibres. These had the look of being struck with light- 

 ning. On the other hand, the arterial blood of the animal 

 grew black, ill-supplied with oxygen, overloaded with car- 

 bonic acid, and assumed the look of venous blood. Yet in 

 this state the blood has not lost its physiological properties, 

 and under the influence of a new supply of oxygen can re- 

 gain its normal state, and grow ruddy again. The heat, 

 provided the degree be not too elevated, only promotes 

 activity in sanguine combustion, without changing the blood. 

 Nor does the nervous system either appear to suffer much. 

 The element most deeply affected is muscle ; heat is a poi- 

 son of the muscular system, like sulpho-cyanuret of potas- 

 sium, and the upas-antiar. It is the loss of the vital proper- 

 ties of this system which, by bringing about rigidity of the 

 muscles, then the stoppage of circulation, and consequently 

 of respiration, is a necessary cause of death. This destruc- 

 tion of the contractile muscular fibre occurs toward 37 or 

 39 in cold-blooded animals, toward 43 or 44 in mammals, 

 toward 46 or 48 in birds, that is, speaking generally, at 

 a temperature five or six degrees higher than the natural 

 temperature of the animal. Bernard calls attention to the 

 fact that in no case is it allowable to suppose that life op- 

 poses a kind of resistance to the excessive heating ; on the 

 contrary, vital movement tends to quicken it, and that may 

 be readily understood. The internal heat produced by the 

 animal unites with the acquired heat, and the renewal of 



