ANIMAL HEAT. 4:15 



establish the numerical value of" certain acts in what are 

 called "mechanical equivalents of heat," or "heat-units." 

 The observations of Beclard possess considerable physiolo- 

 gical interest, but they are useful chiefly, if not entirely, in 

 their positive results. 



Observations upon the influence of mental exertion on 

 the temperature of the body have not been so numerous, but 

 they are, apparently, no less exact in their results. Dr. Davy 

 was the first to make any extended experiments on this 

 point, and has noted a slight but constant elevation during 

 " excited and sustained attention." x More lately, the same 

 line of observation has been followed by Prof. Lombard, who 

 employed much more exact methods of investigation. Prof. 

 Lombard noted an elevation of temperature in the head 

 during mental exertion of various kinds, but it was slight, 

 the highest rise not exceeding the twentieth of a degree. 8 



It is stated, also, that the temperature of the body is in- 

 creased by the emotions of hope, joy, anger, and all exciting 

 passions; while it is diminished by fear, fright, and mental 

 distress. Burdach, from whom the foregoing statement is 

 taken, cites an example of an elevation of temperature from 

 96 to 99*5 in a violent access of anger, and a descent to 

 92*75 under the influence of fear, but the temperature soon 

 returned to 9T'25. 3 



The nervous system exerts a most important influence 

 over the animal temperature, as it modifies the circulation 

 and the nutritive processes in particular parts. The most 

 interesting of these influences are transmitted through the 

 sympathetic system. These will be discussed, to a certain 

 extent, in connection with the theories of calorification ; but 

 they cannot be taken up fully until we come to consider the 



animale. Archives generates de medecine, Paris, 1861, 5me serie, tome xvii. 

 The conclusions in this interesting memoir are to be found on page 277, et seq, 



1 DATY, Physiological Researches, London, 1863, pp. 19, 51. 



2 LOMBARD, Experiments on the Relations of Heat to Mental Work. New York 

 Medical Journal, 1867, vol. v., p. 198, et seq. 



3 BURDACH, Traite de physiologic, Paris, 1841, tome is., p. 645. 



