428 



Dr. W. Marcet. 



[Feb. 10, 



It will be observed, first of all, on considering these figures, that 

 both in my case and M. David's much less air, reduced, or a smaller 

 weight of air, was expired per minute, and consequently breathed at 

 11,030 feet above the sea than at 1,230 feet; this difference was in my 

 case by 29'2 for 100 expired at 1,230 feet, and withM. David's by 28=0 

 per cent. ; and it is not a little remarkable that the difference per 

 cent, in both cases should be all but the same. There is also a falling 

 off of the volume of air (reduced) I exhaled at Courmayeur, but 

 M. David expired much the same amount at both stations. In v my 

 former experiments at Teneriffe and in the Alps I also observed a 

 reduction in the volume of air expired (reduced) at high altitudes, so 

 that there can be no doubt that, although the actual volume of air 

 breathed is greater because of its being rarefied, still a smaller iveight 

 of air is breathed within a given time in the mountains than in the 

 plains. 



I shall now beg to consider the volume of air expired for 1 grm. of 

 carbonic acid at our various stations — a subject interesting both in a 

 physiological and medical point of view. In my case, the proportion 

 of air breathed for 1 grm. C0 3 expired falls steadily from our lower to 

 our higher station ; or, in other words, at Courmayeur I required a 

 weight of 8*6 per cent, less air to make 1 grm. of carbonic acid than at 

 Yvoire ; and at the summit of the pass I inhaled a weight of air as 

 much as 14*0 per cent, smaller to produce 1 grm. of carbonic acid than 

 at the lowest station. In M. David's case there is a decrease of 8 per 

 cent, in the weight of air expired at the summit of the Col for 1 grm. 

 C0 3 compared with that expired near the Lake of Geneva. At the in- 

 termediate station (3,945 feet), however, there is a slight increase ; the 

 rule remains, nevertheless, I consider, as well proved, that at certain 

 altitudes, which may vary with different persons, a smaller weight of 

 air is required to yield the necessary oxygen for producing in the body 

 the same weight of carbonic acid ; this law also held good on 

 my former experimental stations. It accounts, in my mind, for the 

 immunity against consumption met with amongst the inhabitants of 

 towns and villages at elevations beyond 4,000 or 5,000 feet above 

 the sea, and for the beneficial influence exercised in some cases on 

 the progress of phthisis by such high places as Davos in Switzerland. 

 At these stations a smaller weight of air is required for the produc- 

 tion of carbonic acid than in the plains, which means that the air 

 breathed passes through the substance of the lungs into the blood 

 more readily at certain altitudes than it does nearer the sea-level ; 

 and, consequently, where the pulmonary organ is unequal to a free 

 diffusion of air through its tissue, as is the case in consumption, and 

 probably in old- standing bronchitis, such an. influence of altitude on 

 respiration is likely to produce a favourable change. M. Mermod, whose 

 interesting inquiries on the effects of altitude upon respiration I 



