360 Dr. W. Marcet and Mr. E. B. Floris. The Efficiency 



" The Efficiency of Man, or Economic Coefficient of the Human 

 Machine." By W. MARCET, M.D., F.K.S., and E. B. FLORIS 

 F.C.S. Eeceived February 3, Eead February 23, 1899. 



(From the Physiological Laboratory, University College, London.) 



In a paper communicated by one of us, in April last, to the Eoyal 

 Society,* a calorimeter was described for determining the heat emitted 

 by man, whieh, on being tested, was found to give very reliable results. 

 At the same time a short history was added of the various instruments 

 used by physiologists to estimate the heat given out by man and 

 animals; from that list was accidentally omitted the calorimeter of 

 D'Arsonval.f 



This calorimeter consists of two cylindrical concentric vessels, with 

 an air space between them, and standing in an annular groove full of 

 water, thus making an air-tight joint. The outer chamber (annular 

 space) has a manometer connected with it which registers in a graphic 

 way the variations of pressure in that chamber throughout the experi- 

 ment. The subject of the experiment is enclosed in the inner chamber 

 into which fresh air is continually being drawn by means of a flue 

 where a gas burner is kept alight. The whole apparatus is suspended 

 from the ceiling by a pulley, and balanced with a weight. It might be 

 recollected that Marcet's calorimeter which we made use of, consists of 

 a wooden chamber covered with felt inside and out, enclosing another 

 made of sheet copper, carefully polished inside, with an air space 

 between them. The size of the inner chamber is sufficient to admit of 

 a person sitting down comfortably on a chair, with free elbow and head 

 room. Two ventilators (agitators), worked by electric motors, con- 

 stantly mix up the air inside the calorimeter, while the air from one of 

 these ventilators impinges on a trough full of ice ; the water from the 

 melted ice is collected in a flask, and its temperature read at the end of 

 the experiment. 



Thermometers with stems projecting above the chambers show the 

 temperature of the air in the copper chamber and the annular space, 

 and another gives the temperature of the copper walls ; these thermo- 

 meters are divided into fiftieths of a degree centigrade. For further 

 particulars we beg to refer to the original paper. The amount of heat 

 evolved is easily calculated from the weight of ice melted, the tem- 

 perature of the resulting water, and the change of temperature of the 

 chamber, the annular space, and the copper. 



Test experiments, made by means of the combustion of hydrogen 



* "A Calorimeter for the Human Body," by W. Marcet, ' Eoy. Soc. Proc.,' 

 Tol, 63. 



t ' Trayaux du Laboratoire de Marey,' 1878-79. 



