4 i2 THE POPULAR SCIENCE MONTHLY. 



same point of view, and ascertained that the effect produced varies 

 with individuals. Thus from 49 to 58 the stove grew insupportable 

 to Delaroche himself, who became ill from the experiment, while Ber- 

 ger was scarcely fatigued by it. On the other hand, Berger could re- 

 main only seven minutes in a medium heated to 87, while Blagden 

 stayed 12 minutes in it. In tropical countries the heat often rises during 

 the day above 40 without troubling the natives. At the Cape of Good 

 Hope the thermometer marks 43. Yet sometimes such a heat is 

 murderous. It is related, among other cases, that in the month of 

 June, 1738, in the streets of Charleston, several persons died under 

 the influence of 41. In Africa our soldiers are often known to be at- 

 tacked with madness and to die in making a long: march, under the 

 rays of a burning sun, but here the influence of light is combined with 

 that of heat. Duhamel mentions the account of several servant-girls 

 of a baker, who could remain without any inconvenience at all for 

 nearly ten minutes in an oven heated to the necessary degree for bak- 

 ing bread. The experiment has since been repeated. There is noth- 

 ing contradictory in these facts. An animal can endure for some time 

 a temperature much higher than its own, because the very profuse 

 transpiration which occurs in such a case prevents the heating of the 

 organs ; yet, as we shall see, so soon as the internal heat really rises a 

 few degrees above the normal figure, life is no longer possible. 



The study of these phenomena had scarcely been carried further, 

 when in 1842 Claude Bernard devoted to it certain researches, which 

 he resumed and finished last year, and of which he has just published 

 the results. This physiologist used a pine box, divided into two parts 

 by a grating, on which the animal subjected to the experiment is 

 placed. The box rests on a cast-iron plate, and the whole is arranged 

 on a furnace which warms the air of the apparatus more or less. A 

 window, placed in the side of the box, allows the head of the animal 

 to be fixed outside of it at will. Examining animals, subjected under 

 these conditions to the influence of air more or less warm, Bernard 

 verified the first observations of Berger and Delaroche, and made new 

 and more important ones. Boerhaave had given as the cause of death 

 the application of hot air to the lungs, preventing the cooling of the 

 blood. Bernard showed by experiments that hot air, acting on the 

 skin, creates a rise of temperature more rapidly fatal than when this 

 fluid is merely introduced into the pulmonary vessels. He proved also 

 that, when the hot air is damp, the phenomena take a more rapid 

 course, and death occurs much more quickly and at a lower tempera- 

 ture than in dry air. This difference must result from the fact that 

 dampness promotes a rise in temperature. 



When an animal is subjected to the poisoning effects of heat, it 

 presents a series of uniform and characteristic phenomena. It is at 

 first a little disturbed, then panting, its movements of respiration and 

 circulation accelerate, it grows slowly hotter through the circulation, 



