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



two liigliest stations on Teneriffe, above the amount expired at the sea- 

 side, is only 1-2 per cent., which is so small as to he hardly worth 

 recording. In the Alps, at altitudes somewhat corresponding with 

 those of the Teneriffe station, but in a much colder climate, the excess 

 of carbonic acid expired at the highest over the lowest station was 

 15 per cent., while, if the mean of the four high stations over the 

 fifth or lower station be taken, it will give an excess of 8'1 per cent. 



In the case of the guide, there is not only no increase of carbonic 

 acid expired in the high stations, but we find a considerable increase 

 at the lowest station (above the two others), where the heat felt, and 

 consequently absorbed, was the greatest; this increase amounts to 17*8 

 per cent. 



The mean volume of air expired, reduced to 32° and the seaside 

 pressure, was observed in my case to fall by 14*5 per cent, from the 

 lowest to the highest station. With the guide there is also a decrease 

 of air expired under similar circumstances by 16*1 per cent. 



I find the percentage of carbonic acid in the air expired to increase 

 an my case from 4'1 per cent, at the lowest station to 4' 9 per cent, at 

 the highest, while with the guide the proportion of carbonic acid in 

 the air exhaled is nearly the same at his three stations. 



The frequency of my respiration undergoes a marked reduction at 

 the seaside, though nearly the same at my three high stations ; the 

 reduction amounts to no less than 31*2 per cent. In the case of the 

 guide, the mean number of respirations per minute is exactly the same 

 at his two high stations, but also falls off at the seaside by 25*5 per 

 cent. 



In all these experiments air was breathed through a mouth-piece, 

 and on that account the rate of breathing was a little slower and 

 apparently rather deeper than if no mouth-piece had been used. The 

 same method was pursued in every experiment, so that the results may 

 be compared with each other with all due regard to strict accuracy. 



Respiration during a Measured Amount of Muscular "Exercise. 

 In my former communication, I related a certain number of experi- 

 ments referring to the increased expiration of carbonic acid while in 

 the act of ascending. Since then it occurred to me that an inquiry 

 into the amount of carbonic acid expired during a well-regulated 

 walking exercise would yield interesting results. From the difficulty 

 of regulating exactly the degree of muscular power exerted while 

 walking, it occurred to me that some arrangement, on the principle of 

 a tread- wheel, was more likely to answer my purpose, and I finally 

 adopted the tread-boards or rocking-boards described at the beginning 

 of the present communication. While using these boards we raised a 

 weight of 39*5 lbs. forty-five times per minute, as measured by a 

 metronome, to a height of 5"06 inches for every step. 



