1879.} Various Altitudes on the Island and Peak of Tenerijfe. 503 



•chest, liave a height in boots with moderately thick soles of 5 feet 

 7f inches, and weigh 70 kilog., say 11 stone. We are both in the 

 enjoyment of very good health. 



It will be observed that we lived precisely in the same way, were 

 exposed to the same kind of atmospheric influence, and ate the same 

 kind of food, although from the weight of his body, the guide con- 

 sumed more than I did. The amounts of carbonic acid we expired 

 could therefore be fairly compared with one another. 



The mean weight of carbonic acid expired from sixty experiments 

 for myself, and fifty-five for the guide, both sitting, and at the 

 same stations respectively, was in my case, 472 mgms. per minute, 

 and in that of the guide 604 mgms., or on 100 kilos, weight of 

 my body, I expired 674 mgms. of carbonic acid per minute, and the 

 guide also on 100 kilos, weight, 679 mgms. Thus it was found that 

 we both gave out at the lungs an amount of carbonic acid propor- 

 tional to the weight of our body. This is an interesting, though not 

 unexpected result, which appears to me to give much weight to the 

 correctness of the investigation, and consequently to the reliability of 

 the conclusions. 



Another circumstance in connexion with the present work still 

 more deserving of notice than the former, was the fact that while we 

 •were engaged raising at each step a weight of 39" 5 lbs. with the feet, 

 on rocking boards, at the rate of 45 steps per minute, as will be sub- 

 .sequently described, a mean amount of carbonic acid was expired by 

 each of us respectively, again proportional to the weight of our body. 

 In these experiments, the mean weight of carbonic acid obtained for 

 myself from eighteen experiments, six at three different stations, was 

 l'Oll grms. per minute, and for the guide from the same number of 

 -experiments at the same stations 1'269 grms., giving for myself for 

 100 kilos, of body, 1'444 grms., and for the guide for 100 kilos, of 

 body 1'426. Nothing can be more conclusive ; we again produced 

 within our bodies as nearly as possible the same amount of carbonic 

 acid proportionally with our weight. These figures also show that 

 the method adopted was well calculated to give reliable results, while 

 ■ engaged in a definite amount of muscular exercise. 



Amount of Carbonic Acid expired at the different Stations. 

 The mean amount of carbonic acid expired at the several stations 

 by both of us in the sitting posture, was found, to a great extent, to 

 be influenced in a similar way by the food taken. In both cases, with 

 but one exception, the greatest amount of carbonic acid expired was 

 during the first or second hour after eating, and the quantity 

 diminished as time elapsed from the last meal taken. * The exception 



* Dr. Edward Smith's (" Phil. Trans.," 1859) experiments show that a minimum 

 .amount of carbonic acid expired is obtained while fasting, beyond which continued 

 fasting, within certain limits, produces no further reduction. 



