402 THE POPULAR SCIENCE MONTHLY. 



a poverty of the blood-corpuscles in oxygen, wliich. lie believed to 

 be a result of the feeble pressure of the atmosphere in those re- 

 gions. In the study of the question of the influence of atmospheric 

 pressure on health, which he was led by these observations to un- 

 dertake, he availed himself of the aid of M. Bert's experimental 

 skill. M. Bert performed a long series of experiments upon small 

 animals exposed to atmospheres of various pressures. The book 

 in which he gave an account of them includes full reviews of ex- 

 cursions into great altitudes, of observations on mountain-sick- 

 ness, and of balloon ascensions to great heights. An experimental 

 ascension in the balloon Zenith was made in 1875 in aid of this 

 investigation, its special object being to determine the quantity 

 of carbonic acid contained in the atmosphere at an altitude of 

 twenty-four thousand feet. Three persons went up in the balloon, 

 two of whom, M. Sivel and M. Crocd Spinelli, perished at a height 

 of about twenty-four thousand feet, from the effects of the rare- 

 fied air, while the survivor, M. Gaston Tissandier, was made in- 

 sensible for a considerable length of time. The main cause of the 

 disaster was believed to be "the vertigo of high regions," by 

 which the aeronauts were excited to throw out ballast and go 

 higher, when prudence should have dictated to them to descend. 

 The main object of the expedition was not attained, because the 

 instruments also were thrown out and broken. The balloon 

 reached a height of eight thousand six hundred metres, as was 

 shown by the maximum barometers. The results of Prof. Bert's 

 experiments were published in 1878, in his work " La Pression 

 baromdtrique ; Recherches de Physiologie expdrimentale " (" Bar- 

 ometric Pressure; Researches in Experimental Physiology"). 

 Among his principal conclusions were those that the diminution 

 of barometric pressure acts on living beings only by diminishing 

 the tension of the air which they breathe, in the blood which ani- 

 mates their tissues, and by thus exposing them to the dangers of 

 asphyxia ; that the increase of atmospheric pressure acts only by 

 increasing the tension of the oxygen in the air and the blood ; 

 that the inconvenient effects of diminution of pressure may be 

 efficaciously combated by the respiration of an air sufficiently 

 rich in oxygen to maintain the tension of that gas at its normal 

 value, and those of the increase of pressure may be combated by 

 employing air sufficiently poor in oxygen to arrive at the same 

 result ; that the beings actually existing in a wild state on the 

 surface of the globe are accommodated to the degrees of oxygen- 

 ated tension under which they live ; that barometric pressure and 

 the proportion per cent of oxygen have not always been the same 

 on our globe — the tension of the gas has apparently been, and will 

 without doubt continue to go on, diminishing ; and that it is inac- 

 curate to teach that plants must have appeared on the earth be- 



