THE HUMAN BODY AS AN ENGINE. 491 



THE HUMAN BODY AS AX ENGINE. 



By Professor E. B. ROSA. 



THERE is no more interesting subject for scientific investigation 

 than the structure and operation, the anatomy and physiology of 

 the human body. That it is an amazingly complex and delicate 

 mechanism, performing a multitude of functions in a wonderfully per- 

 fect manner, is, of course, an old story. That in the assimilation of its 

 nourishment and in the growth and repair of its tissue the body obeys 

 the laws of chemistry has long been understood. But that the body 

 obeys in everything the fundamental law of physics, namely, the law 

 of the conservation of energy, has not been so generally recognized. 

 Eor some years the writer was engaged in some investigations upon this 

 subject. 1 The development of the complex apparatus and unique 

 methods of the research required years of patient labor and study. One 

 of the features of the apparatus was an air-tight chamber, in which a 

 man, as the subject of the experiment, could be confined for any desired 

 period, eating, sleeping, working and living while under minute obser- 

 vation. The experiments usually continued four or five days, but were 

 sometimes prolonged to eight or ten days, and the observations were 

 made and recorded day and night continuously for the entire period. 



The atmosphere within the chamber was maintained sufficiently 

 pure to make a prolonged sojourn within its walls entirely comfortable. 

 A current of fresh air, displacing as it entered an equal quantity of air 

 which contained the products of respiration, was maintained continu- 

 ously. The respired air was analyzed and measured, and the products 

 of respiration from lungs and skin accurately determined. The ven- 

 tilating air current was maintained by a pair of measuring air pumps, 

 driven by an electric motor. The air was dried, both before entering 

 and after leaving the chamber by freezing out its moisture. This was 

 done by passing it through a refrigerator where its temperature was re- 

 duced far below the freezing point. The refrigerator was operated by 

 an ammonia machine, driven by an electric motor. The quantity of 

 air was automatically recorded by the pumps. 



The chamber was so constructed and fitted with electrical and other 

 devices as to afford the means of measuring the quantity of heat which 

 the subject of the experiment gave off from his body. And in order to 

 keep the temperature of the room constant this heat was absorbed and 

 carried away by a stream of cold water, the latter flowing through a 



'The work was done at Wesleyan University, in collaboration with Prof. W o. Atwater, 

 under the patronage of the University and the U. S. Department of Agriculture. 



