174 REPORTS ON THE STATE OF SCIENCE. . 



Mental and Muscular Fatigue. — Report of the Committee, consisting of 

 Professor C. S. Sherrington {Chairman), Dr. W. McDougall 

 (Secretary), Professor J. S. MacDonald, Mr. H. Sackville 

 Lawson, and Dr. J. E. Chapman. 



The Committee report that Professor MacDonald and Dr. J. E. Chap- 

 man have been working during the past year with the large calorimeter 

 of the Sheffield University physiological laboratory and have made good 

 progress in mastering the many difficulties involved in exact determina- 

 tion of heat production in the human body. A statement of the nature 

 of their work is appended. Mr. Sackville Lawson has continued his 

 investigation into mental fatigue in schoolboys. The sum of 91. has 

 been assigned to him in order to complete the purchase of the Rivers- 

 McDougall fatigue-apparatus which he is using. The remainder of the 

 grant of 251. has been assigned to Professor MacDonald and Dr. Chap- 

 man to defray expenses of their calorimetric research. 



Report to the Committee. By Professor J. S. MacDonald and 



Dr. J. E. Chapman. 



We report a year spent in the development and use of a calorimeter 

 built, as far as its body is concerned, on the plan, and with the dimen- 

 sions, of the Middletown calorimeter of Atwater and Benedict. In 

 many minor details, however, we have found it useful to depart from 

 that plan, as in the construction of the radiator systam, the resistance 

 thermometers, &c. 



Not intending to measure the respiratory exchange of gases at 

 present, we are freed from limitations due to the dimensions and resist- 

 ance of absorption apparatus. We have thus used a greater air-flow, 

 the pump now in place drawing 450 cubic feet per hour through the 

 calorimeter. This air passes into the chamber without preliminary 

 treatment other than modification of its temperature to suit that of the 

 calorimeter, and in this increased air-flow and its normal character we 

 have obtained certain advantages. 



Our arrangements for each experiment have been greatly facilitated 

 by the discovery of a relationship between the heat output within the 

 chamber and the temperature of the calorimeter and radiator system 

 such that 



H 



( T --H^) 



where H is the heat output, T is the temperature of the calorimeter, 

 and T a and T, the temperatures of the water entering and leaving the 

 radiator system respectively. This equation, containing as it does no 

 quantity concerned with the rate of water flow, has been of considerable 

 use. For a physical explanation of this observed fact we have to thank 

 Mr. J. Robinson, M.Sc, Ph.D. 



Using the calorimeter simply for the purposes of heat measurement, 

 and not as a respiration calorimeter, we have had to deal with water 

 vapour leaving the instrument solely as it affected the heat equations, 



