Theories and Experiments 225 



in the blood, which, moreover, would be "unchemical" and incom- 

 patible with life, for at the slightest increase in temperature or 

 decrease in pressure, nothing could prevent the escape of these 

 gases. 



It is curious to see, a few years afterwards, a celebrated French 

 physician, Rostan, 42 appeal to the very influence of these gases, 

 though vaguely, it is true, to explain the symptoms of decompres- 

 sion. He mingles with his discussion the mistaken ideas, which we 

 have already met and which we shall often find again, about the 

 part played by the decrease of the weight sustained by the body: 



If one places a living animal in a vacuum, the air within, having 

 nothing to resist it, expands, the animal swells up and dies ... It is 

 the pressure of the air which keeps the fluids in the vessels of animals 

 and prevents them from escaping. When the barometer drops a few 

 degrees, the fluids press towards the periphery; there is difficulty in 

 breathing, disturbance of the circulation, and congestion towards the 

 head. (P. 340.) 



About this same time there appeared an English memoir which 

 at least had the merit of originality, in the sense of oddness. Cun- 

 ningham, 43 as Govan had already done, makes electricity play a 

 principal part, thus explaining the unknown by the unknown; but 

 he adds a strange idea; that there is a radical difference between 

 the effects of the ascent of mountains in the two hemispheres: 



Apoplectic symptoms characterize the distress of travellers on 

 Mont Blanc, whereas in the southern hemisphere the threatening 

 symptoms are all those which accompany syncope . . . 



The first have been attributed to the great rarefaction of the air 

 which permits the soft parts of the human body to expand as a result 

 of the reduction in the pressure exerted upon them; but since a similar 

 elevation in the Andes produces effects of an opposite nature, we 

 should seek to explain the latter by other causes than the rarefaction 

 of the air. 



This cause the author finds in electricity, 



Which occupies, in the northern hemisphere, the upper part of the 

 body, and, in the southern hemisphere, the lower part, and thus tends 

 to draw the blood towards the head in the former, and towards the 

 feet in the second . . . which also explains why the distress is re- 

 lieved by the horizontal position. 



We think it useless to continue any farther, and we shall also 

 report without comment the few lines which Burdach, 44 in his im- 

 mense encyclopedia, devotes to the effects of a decrease in pressure 

 upon the organism; we see clearly by what he says that he 



