506 Dr. W. Marcet on the Function of Respiration at [Apr. 24,. 



It will be observed in this table, that, in my case, when approxi- 

 mately equal altitudes in the Alps and on the Peak of Teneriffe are 

 compared as to their influence on respiration, at the highest stations 

 there is an increase of carbonic acid expired by 13'8 per cent, for 

 Teneriffe ; at the stations next in altitude, the increase is by 9 "6 per 

 cent, for Teneriffe, and at the seaside, compared with the shores of 

 the Lake of Geneva, the enormous increase for Teneriffe of 18'7 per 

 cent, is noted. As to my guide, I have, unfortunately, but few 

 experiments on the carbonic acid he expires on the Alps, which only 

 amount to four in number. They show for approximately equal 

 altitudes no increase of carbonic acid expired on the Peak of 

 Teneriffe ; but at Puerto de Orotava I find him to give out a very large 

 quantity of carbonic acid in excess of that he expired in the Alps, 

 amounting to as much as 17' 5 per cent. There are no determinations 

 of the carbonic acid expired by the guide at the altitude of Geneva, 

 to compare with those obtained at the seaside on the Island of 

 Teneriffe, but the increase at Teneriffe is greatly beyond any result 

 that might have been expected at the lowest northern station. 



If my excess of carbonic acid expired on the Peak of Teneriffe, 

 over the amount expired in the higher Alps amounts to 13" 8 per cent., 

 while there is no increase in the case of the guide, this is probably 

 owing to the guide apparently perspiring much more freely than I do, 

 and to the circumstance that his home is in the mountains, while I am 

 accustomed to a residence at the sea level. 



This fact, that an excess of carbonic acid is expired in hot climates 

 over that given out in temperate zones, is to me so unexpected, and, 

 indeed, so different from what might have been anticipated, that I 

 feel bound to give every possible proof of the accuracy of my work. 



An objection might be raised to the correctness of the analysis from 

 changes occurring in the normal solution of barium from the action 

 of the carbonic acid of the air. This was carefully guarded against ; 

 the whole contents of one small bottle were used for each analysis, 

 thus avoiding the necessary introduction of air in opening the bottle 

 had the stock of the alkaline solution been carried in a single large 

 flask. The normal solution was seen to be perfectly clear when 

 poured into the 100 cub. centim. pipette, although it had travelled 

 all the way from London to Teneriffe, and been carried on mule-back 

 to near the summit of the Peak. But a circumstance still more con- 

 vincing of the satisfactory state of the solution of barium was 

 derived from the examination of a bottle of this solution, which had 

 accidentally escaped being used at Teneriffe, and was found after my 

 return on unpacking the basket. The solution in this bottle exhibited 

 a small number of white specks at the bottom, there were so few that 

 on shaking the solution looked clear ; on standing the specks re- 

 appeared. I subjected this fluid to a careful analysis. 25 cub. centims. 



