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The air from the lungs was expired into a strong india-rubber bag of a known capacity under a pressure of one inch of water. The bag used in nearly every experiment sitting held 39.3 litres of air under that pressure; and in the experiments made while engaged with a measured amount of muscular work, a bag holding 68-4 litres of air under the same pressure was employed.

The tube into which the expired air was drawn for analysis was supplied with the india-rubber diverticulam described in my former communication, and I made occasional use of it to take out smali quantities of air and test them with a solution of barium hydrate. I thus observed that a continued agitation of five minutes sufficed for the entire combination of the carbonic acid. In every experiment the agitation was continued for six or seven minutes or longer, by the watch. The bottles, into which the fluid was drawn after agitation, were well corked, and their necks dipped into melted paraffin, Although large enough for somewhat more than the bulk of the fluid they contained, the empty space was too small for the air it held to affect the alkaline solution.

My Chamounix guide was practised in the mode of breathing into the bag, so that I could rely upon his doing this in a perfectly natural way, and without the loss of any of the air expired; he was also in the habit of counting his expirations while so engaged.

We assisted each other mutually; one of us keeping an eye on the stop-watch and the bag, while the other was breathing into it. After sitting quiet for a few minutes, the mouth was applied to the mouthpiece, and at the very beginning of the first expiration, a sign was made and the stop-watch started. When the bag was nearly full, the water in the gauge began to rise, and the instant it attained the height of one inch, the watch was stopped. The time to fill the bag was then read off, and the temperature of the air in the bag ascertained, both observations being immediately noted. Without any loss of time the air was at once aspired into the cylinder, and its temperature within the cylinder again read off by means of a thermometer run through the india-rubber stopper.

Then followed the introduction of the normal alkaline solution, the agitation and the bottling; a whole experiment took from thirty minutes to forty-five or fifty minutes. The total number of my Teneriffe experiments on respiration, including the determination of the carbonic acid expired, amounted to 157.

The Chamounix guide is a tall and very powerful man of 38 years of

age; I found him to measure round the bare chest at the nipples, 3 feet 5 inches. His height, in boots with moderately thick soles, is 6 feet 04 inch, and he subsequently found his weight to be 89 kilog., -exactly 14 stone.

I am 50 years of age, measure 2 feet 10inches round the bare


chest, have a height in boots with moderately thick soles of 5 feet 74 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 consumed 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

both gave out at the lungs an amount of carbonic acid proportional 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 subsequently 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 inyself from eighteen experiments, six at three different stations, was 1:011 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 refers to the guide at Puerto, where his maximum is found to be during the third hour after a meal. The fluctuations in my case may be said to follow closely those formerly reported from my experiments in the Alps.

* 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.

The subjoined table shows at a glance the variation of the mean amount of carbonic acid expired during each successive bour after food, the fifth or sixth hour being grouped together for want of a sufficient number of experiments.

Table showing the Influence of Food on the Expiration of Carbonic Acid at the various Stations (in the sitting posture).

Self sitting.

Hours after Food.

Alta Vista.

CO, expired per CO, expired per co, expired per


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The figures between brackets refer to the number of experiments. One experiment, at 5.48 A.M. at Guajara, not included.

If the figures reported in this table be taken into consideration together with the corresponding results obtained in the Alps, it will appear that the maximum amount of carbonic acid is expired rather earlier after a meal on the mountains than in the plains, which would show that there is apparently a tendency to a more rapid digestion and assimilation of food in the mountains than near the sea level.

As in the case of my former investigation, I have neutralised as much as possible the influence of food on the results of the experiments, by conducting the inquiry at all times of the day between breakfast and bedtime.

Influence of Temperature on the Carbonic Acid erpired.--So far, to my knowledge, the only series of observations we possess on the influence of tropical climates on the functions of the human body, are those of Dr. Rattray, Surgeon R.N., who has clearly taken great pains to investigate the subject; he concludes that :

The three marked tropical phenomena, viz., diminished lung vascularity, slower respiration, and gentler breathing are closely related, and together indicate reduced lung work, the reverse for the temperate zone marking an increased function,* &c.”

Dr. Rattray infers, without apparently making any actual determination of carbonic acid in the air expired, that there is a larger amount of carbon thrown out by the lungs in temperate than in tropical climates. The consideration of the mechanical action of heat, with reference to the functions of the body, had led me long ago to adopt the same views; and previous to my Teneriffe experiment, I had believed that where the heat of the sun was in excess, less heat was required to be manufactured by the body for the due performance of its functions, and, consequently, less carbonic acid was formed and given out. I am now compelled, however, to alter this view, and to conclude that more carbonic acid is formed in the body under a tropical or nearly tropical sun than under temperate latitudes.

In order to make the subject perfectly clear, I have placed, in a tabular form, the figures showing the amount of carbonic acid expired, as found by direct experiments both in my Alpine and southern stations. Table showing comparatively the Weights of Carbonic Acid and the

Volumes of Air (reduced) expired per minute by myself and guide in the Alps and at Teneriffe.

Self sitting.

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The figures for the weights of CO, expired in the Alps have undergone a correction. See foot-note, page 507.

* “Proc. Roy. Soc.,” vol. xxi, 1872.

It will be observed in this table, that, in my case, when approximately 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 convincing 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 reappeared. I subjected this fluid to a careful analysis. 25 cub. centims.

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