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'8 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- 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 ll° - 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°45. 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 l c -8, 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 0- 8 and 38 o, 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 o, 3 to 1°, while 
Hobday s 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 Xewport 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. r j)hys. et nat., Geneve, tome xxxvi. p. 247. 
2 Marcet, Croonian Lectures, Brit. Med. Journ., London. 1895, vol. i. p. 1367. 
3 "Der Hitzscblag," Bonn, 1867, S. 80. 
4 St. George's Hosp. Rep. , London, 1866, vol. i. p. 232. 
5 Crombie, Indian Ann. Med. Sc, Calcutta, 1873, vol. xvi. p. 579; Roger, " Re- 
cherehes cliniques sur le.s maladies de l'ent'ance," tome i. p. 227 ; Speck, Arch. d. Ver. f. 
gemeinsch. Arb. z. Ford. d. ivissensch. Heilk., Gottingen 1862, Bd. vi. S. 161-324; Cuny 
Bouvier, Arch. f. d. ges. Physiol. , Bonn, 1869, Bd. ii. S. 386. 
6 Ellenberger, " Vergleichende Physiologie der Haussaugethieie," 1892, Bd. ii. Th. 2, 
S. 87. 
7 Deutsche Ztschr. f. Thiermed., Leipzig, 1875, Bd. i. S. 87. 
8 Journ. Camp. Path, and Therap., Edin. and London. 1S96, vol. ix. p. 286. 
9 Phil. Trans., London 1837, pt. 2, p. 259. 
10 Ibid., 1845, pt. 2, p. 319 ; 1850, p. 443. 
