290 Chronicles of Science. [April, 



12. ZOOLOGY— ANIMAL PHYSIOLOGY AND 

 MOEPHOLOGY. 



Physiology. 



Researches on the Relation of Heat to Work in the Human Body. — 

 Professor Pettenkoffer, of Munich, has undertaken an investigation 

 into the amount of heat produced by the human body when at rest 

 and when at work, which promises to give highly important results. 

 The wonderful experimental chamber which King Max had con- 

 structed for Pettenkoffer's work is to be made use of. The chamber, 

 which is about 10 feet square, is fitted with an iron tube through 

 which the air is regularly drawn by means of an aspirator worked 

 by a steam-engine, the air being accurately measured in a gas 

 meter. Smaller aspirators bring measured quantities of the air 

 through analysis- tubes in which the quantities of carbonic acid, water, 

 hydrogen and carburetted hydrogens (the last two by combustion 

 with spongy platinum) are determined in the air both before and 

 after it enters the chamber. The small aspirators, bringing a small 

 but constant fraction of the whole air passed into the chamber 

 through the analysis apparatus, the quantities of carbonic acid gas, 

 water and hydrogen in the whole can be readily calculated. It is 

 now intended to take the temperature of the air before and after it 

 traverses the chamber, and in this manner to ascertain the actual 

 amount of heat produced by the human body when at rest and when 

 at work, and in relation to the amounts of the various excretions. 

 For this purpose a smaller chamber has been constructed within the 

 first made, and arrangements adapted by means of non-conductors, 

 &c, to prevent, as far as possible, the loss of heat. It is found that 

 there is a constant loss of about 40 per cent, of the total heat with 

 two candles burnt in the chamber ; of about 50 per cent, with four. 

 The heating effect upon the air passed through the apparatus is deter- 

 mined before each experiment with stearine candles of known weight, 

 and thus when a man is placed in the chamber instead of the candles, 

 you get his heating effect in terms of stearine candles, and this is, 

 of course, at once convertible into units of heat. The preliminary 

 experiments with candles promise very accurate and satisfactory 

 results from this method. As an apparatus for chemical analysis 

 the chamber is perfect ; so perfect that the percentage composition 

 of a candle can be determined as accurately by burning it in the 

 chamber, and the fractional analysis, as by the most complete direct 

 combustions. The determination of the heat produced is a matter 

 of more difficulty on account of the fluctuations of external tem- 

 perature and the delicacy of the thermometers which must be used ; 

 but Professor Pettenkoffer has used every precaution, and succeeded 

 in rendering the apparatus efficient. The experiments are now in 



