INFLUENCE OF MENTAL WORK. 807 



is further supported by the fact that Lortet found a few minutes' rest sufficient 

 to raise the temperature to the normal. 



Marcet, 1 shortly before Lortet's observations, found that during an ascent of 

 some of the Mont Blanc chain of mountains the temperature of his mouth fell. 

 This result was contested by Vernet, who had determined the rectal tempera- 

 ture under similar circumstances, and, as the result of the controversy, Marcet 

 and Vernet' 2 in 1888 ascended together one of the highest points of the Jura. 

 They found that there was a distinct rise in. the rectal temperature. Marcet, 

 however, does not look upon this result as conclusive ; he attempts to explain 

 the rise of temperature as due to congestion of the hsemorrhoidal vessels. It 

 must be pointed out, however, that the increased circulation due to exercise 

 would probably not cause congestion, and, whether it did or not, the rise in 

 the temperature of the rectum indicates a rise in the temperature of the 

 internal parts of the body. Further, Marcet himself shows that cooling the 

 under surface of the chin causes a fall in the temperature of the mouth, and 

 this was probably the cause of the low readings observed in his first ascents. 



Obernier 3 found that a walk for thirty-five minutes/ when the 

 external temperature was 11 0< 2, raised the rectal temperature from 37 

 to 38. A walk of five miles raised the temperature of Ogle's mouth 

 from 37 to 37'4o. 4 Similar results have been obtained by others. 5 



Similar results to the above have been obtained upon animals. The 

 temperature of a dog during the first hour of work upon a treadmill was 

 raised 1'S, but although the work was continued the temperature quickly 

 fell (U. Mosso). 6 In the case of two stallions three years old, Liska 6 found 

 the temperature before work 37'8 and 38'0 respectively; after 

 fifteen minutes' work, 39'5 and 39; and again, after twenty minutes' 

 rest, 37'7 and 38. Siedamgrotzky 7 found that exercise raised the 

 temperature of horses by an amount varying from 0'3 to 1, while 

 Hobday 8 found in the case of healthy omnibus horses that the rectal 

 temperature was generally raised 2 or more by hard work, and in sheep 

 and pigs the exertion of running caused a similar rise in temperature. 



Further details of the production of heat in muscle will be given 

 later. 



In the case of insects the effect of muscular activity is very marked. 

 Thus Newport 9 found the temperature of the abdomen of a very active humble- 

 bee (Bombus terrestris) to be 23, when the air was 19 '3 ; four of these active 

 bees placed in a glass bottle raised the temperature of the air from 19 '3 to 

 23-6. 



The influence of mental work. Mental activity is said to have an 

 effect both upon the general temperature of the body and upon the local 

 temperature of the brain and head. Thus Davy 10 found that mental 



1 Arch. d. sc. phys. et nat., Geneve, tome xxxvi. p. 247. 



2 Marcet, Croonian Lectures, Brit. Med. Journ., London, 1895, vol. i. p. 1367. 



3 "Der Hitzschlag," Bonn, 1867, S. 80. 



4 St. Georges Hosp. Rep., London, 1866, vol. i. p. 232. 



5 Crombie, Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. p. 579; Koger, " Re- 

 cherchrs cliniques sur les maladies de 1'ent'ance," tome i. p. 227 ; Speck, Arch. d. Ver. f. 

 gemeinsch. Arb. z. Ford. d. icisscnch. Heilk., Gottirigeii 1862, Bd. vi. S. 161-324; Cuny 

 Bouvier, Arch. f. d. gcs. Physiol., Bonn, 1869, Bd. ii. S. 386. 



6 Ellenberger, " Verglrichende Physiologic der Haussaugethieie," 1892, Bd. ii. Th. 2, 

 S. 87. 



7 Deutsche Zlschr. f. Thicrmed., Leipzig, 1875, Bd. i. S. 87. 



8 Journ. Comp. Path, and Thcrap., Edin. and London, 1896, vol. ix. p. 286. 



9 Phil. Trans., London 1837, pt. 2, p. 259. 



. } 1845, pt. 2, p. 319 ; 1850, p. 443. 



