DESCRIPTION OF APPARATUS FOR TESTING 
THE 
RESULTS OF PERSPIRATION AND RESPIRATION 
IN THE PHYSIOLOGICAL INSTITUTE AT MUNICH. 
BY PROFESSOR MAX PETTENKOFER. 
TRANSLATED FROM THE GERMAN BY PROFESSOR A. TEN BROOK, 
In order to determine the quantity of carbonic acid and water secreted by 
the skin and lungs, various methods have been proposed. The methods of 
Scharling, Vierordt, Valentin and Brunner, Regnault and Reiset, Smith and 
others, with their results, are sufficiently known to every physiologist and 
chemist. What has been justly objected to all methods hitherto applied to 
men and the larger animals has been in reference essentially to two considera- 
tions: first, that the degree of accuracy of the methods had not been ascer- 
tained by test-experiments with known quantities of carbonic acid ;° and second, 
that men and animals had been forced to respire under conditions more or less 
unusual or oppressive, and hence not natural. I have, therefore, for years been 
occupied with the thought of some method for determining with suflicient pre- 
cision the quantity of carbonic acid which a man develops when moving and 
breathing freely without the interposition of any apparatus whatever. The 
investigations of Bischoff and Voit in regard to the nourishment of carnivorous 
animals have shown that the carbonic acid passing off through the skin and 
lungs cannot be with certainty calculated from the difference between the car- 
bon taken in with the food and that eliminated in the urine and excrement, 
taking into account also the weight of the body, because two unknown things, 
carbonic acid and water, escape at the same time and in varying proportions, 
through the skin and lungs. Since, then, there was a necessity for determin- 
ing directly one at least of the two quantities, I resumed the attempt at a solu- 
tion of the problem. I soon perceived that success was attainable only by 
directing over the human body a current of air of measured and constant 
force, and then determining the accession of carbonic acid and water to this 
current of air. It very soon struck me that something like a parlor stove 
might be adopted as a model. As long as the chimney draws, no smoke 
escapes at the joints or door of the stove, but the outside air presses from all 
directions into the stove in order to reach the chimney. If an exact measure- 
ment, in the pipe which conducts the smoke from the stove to the chimney, of 
the amount of air which moves in it is possible; if, further, the composition 
of the air which enters the stove and passes from it can be ascertained from a 
portion of it, then all the factors are obtained which are needed in order to 
determine what admixture the air-current receives from the process of combus- 
tion in the stove. In the plan which I devised the stove is represented by a 
small chamber of sheet-iron, which I shall call the saloon, placed within a 
larger apartment ; the former being eight Bavarian feet in extent each way, 
with light admitted from the top and through windows on the sides. The 
windows should be cemented and the walls and ceiling riveted as nearly as 
possible air-tight. 'The door has movable openings, in order, when necessary, 
to render the admission of air practicable at other points than the joints of the 
