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



It is known, from Dr. Rattray's important researches, alluded to 

 above, that the body loses weight by a change from a temperate to a 

 tropical climate, and recovers its weight on returning into a colder 

 latitude, the loss appearing independent of the amount of food taken. 

 This falling off in the substance of the body, attended, as I have 

 shown, by an increased formation and expiration of carbonic acid, 

 must be due to increased combustion or excessive oxidation. 



It is difficult to offer a theory to explain this phenomenon in our 

 present knowledge of the action of heat on the living body. Cold we 

 know to increase the amount of carbonic acid formed in the body, 

 the object of which is clearly to keep up animal heat to its normal 

 standard ; it is odd indeed that an increase of external heat should 

 ■exert a similar influence. I do not think it necessary to do more than 

 allude to a tendency to looseness of the bowels I had while on the 

 Island of Teneriffe, which I ascribe to the heat of the climate ; the 

 guide informs me there was an opposite disposition with him at 

 Puerto, on the seaside. These minor circumstances interfered in no 

 way with our health, which was quite good, and our work was con- 

 tinued nearly daily, and all day long, during our stay at Teneriffe. 



The following table gives the result, in a condensed form, of the 

 whole of my inquiry on respiration at Teneriffe, in the sitting posture. 

 (See p. 509.) 



The chronological order of my visits to the several stations was — 



1 . Guajara. 



2. Alta Vista. 



3. Foot of Cone. 



4. Puerto de Orotava (seaside). 



The number of experiments made sitting amount, for myself, to 65, 

 for the guide to 55, making altogether 120, and, in each of them, a 

 sample of air expired during from four to six minutes was analysed. 

 The titrations were subsequently all made by myself near Geneva, in 

 the open air, on a balcony, and in order to guard against any acci- 

 dental mistake in the calculations of the analysis, they were all done 

 by myself and an assistant conjointly. 



There was but a very slight increase in the carbonic acid expired at 

 the two highest stations beyond the amount given out at the seaside, 

 and it bore no comparison with the excess of carbonic acid expired at 

 a similar altitude above the sea in the Alps. The mean excess of the 



nected with tlie Alpine experiments, though not with those of Teneriffe, and owing 

 to the circumstance that the solution of common salt used, probably contained a 

 small quantity of alkaline sulphate, the alkali set free by the action of the barium 

 exerted an influence on the titration, apparently increasing the amount of carbonic 

 acid present. Experiments made with three different samples of common salt 

 showed me that the error may safely be limited to 3 per cent., and is certainly much 

 less in many instances. 



