July 2, 1908] 



NATURE 



209 



.4 CALORIMETER FOR DETERMINING THE 



RELATION BETWEEN HEAT-PRODUCTION 



AND MUSCULAR WORK. 

 T N the physiological laboratory of the University of 

 Shefiield a calorimeter has been erected on the model 

 of Atwatcr and Benedict's calorimeter, now carried by 

 Prof. Benedict to a great state of perfection in the Nutri- 

 tion Laboratory at Boston, U.S.A. The Sheffield copy is 

 not at present a complete one, and its limitations are best 

 detailed by a brief description of the problem in the solu- 

 tion of which it is hoped immediately to play some part. 

 'I his problem is the nature of the physicochemical process 

 underlying the phenomenon of muscular contraction, upon 

 which some work has been in progress in this laboratory 

 already along somewhat different lines. 



A precise statement of the relation existing between 

 muscular work and heat production is a necessity for the 

 final solution of this question. Even before precision can 

 be hoped for, additional information may be of much 

 value in deciding the comparative value of different lines 

 of attack. Thus, it having been already shown that the 

 energy liberated is entirely to be assigned to the combus- 

 tion of food, the question arises as to 

 whether the contraction is the direct 

 consequence of the combustion which 

 takes place at the same time, or as to 

 whether it is not rather the conse- 

 quence of some preceding combustion. 

 In the latter case there would be 

 nothing remarkable in the proposition 

 that the combustion responsible was in 

 the main an occurrence taking place 

 during a preceding contraction. Each 

 contraction might, so to speak, \ i'd 

 up a spring for release in the next con- 

 traction. The usual view is that con- 

 traction and the combustion responsible 

 for it are concomitant ; the view of the 

 Sheffield laboratory is that they are 

 not. The second point of view can be 

 at once supported by the well-known 

 fact that fatigued muscle is apparently 

 a more economical heat engine than 

 muscle in good condition, giving off 

 less waste heat for an equal amount 

 of external work done. Such a fact 

 loses all peculiarity if it is considered 

 merely as a failure on the part of the 

 fatigued muscle to provide for succeed- 

 ing contractions. It is in the hope of 

 collecting further data of this kind 

 that the calorimeter has been con- 

 structed. The immediate necessities, 

 therefore, are a calorimeter within 

 which prolonged musrular work can 

 be performed, and from which a 

 complete statement of the amount of work done and 

 heat given off can be obtained. Benedict's original instru- 

 ment offers much more information than this, since it 

 is a complete respiration calorimeter, providing by its 

 use data for a perfect balance-sheet both of chemical 

 material and energy. It is hoped to raise the Sheffield 



of air external to the chamber. The accessory arrange- 

 inents of the calorimeter render it possible to maintain 

 the zinc sheath and the two outer layers of air at the same 

 temperature as that of the copper box, whatever that may 

 be. Heat is thus prevented from escaping from the wall-" 

 of the copper chamber. This end is secured by heating 

 and cooling apparatus in the two outer air spaces, resist- 

 ance wires and cold-water pipes. The degree to which 

 the heating and cooling mechanism is resorted to in each 

 of tliese spaces is determined by the observation of elec- 

 trical currents from one hundred and fifty sets of thermo- 

 couples arranged in two series, a series indicating differ- 

 ences of temperature between the copper and zinc sheaths, 

 another indicating differences between the two outer air 

 spaces. Each series is divided into zones, so that the 

 state of the roof, the floor, or each of three zones in 

 the side walls can be separately observed. The heating 

 and cooling mechanism is similarly subdivided. The 

 observer seated outside the calorimeter can rapidly test 

 each segment of the calorimeter in turn, and rapidly 

 balance any difference found by adjustments of rheostats 

 admitting more or less current to the heating wires, and 

 taps admitting more or less water to the cooling pipes. 



Calorimeter for physiological experiments at Slietfield University. The metal chamber on the 

 left is now enclosed in the wooden house on the right. The spots on the wall of the metal 

 chamber are tubes in which the thermocouples now lie. 



The difficulties in construction up to this point lie mainly 

 in the thermocouples and their fixation. It is a difficult 

 matter especially to prevent risks of short-circuiting and 

 displacement from incapacitating those placed to read 

 differences of temperature between the copper and zin, , 

 since the subject within the calorimeter by movements 



apparatus to the same level of perfection, so that it may causes awkward bulgings of the metal 



be placed at the disposal of investigations of a more general 

 kind when additional financial aid has been obtained. 



The calorimeter has been constructed by Messrs. George, 

 of Birmingham, who have followed the detailed instruc- 

 tions provided by Benedict in the publications of the 

 Carnegie Institution, Washington. At one stage of con- 

 struction it was examined by Prof. Benedict, and then met 

 with his approval. He was kind enough to make 

 iiiiportant suggestions, which have since been carried out. 



.A small room, 8 feet by 6 feet by j feet, has been built 

 of copper sheets carefully soldered together and stiffened 

 by an external wooden framework, to which thev are 

 fixed. On the outer surface of the framework zinc sheets 

 have been fastened, forming a second metal covering. 

 The double-walled metal box so formed rests on rails within 

 a double-walled wooden house enclosing it. Thus the 

 walls, copper, zinc, wood, and wood separate three layers 



NO. 2018, VOL. 78] 



A second difficulty in construction is the necessity for 

 an absolutely air-tight copper chamber admitting no air 

 save through the pipe provided, and allowing none to 

 escape save througli the exit tube. There are a number 

 of apertures which have to be carefully sealed. Thus the 

 window through which the subject enters is subsequently 

 glazed. There is also an air lock through which material 

 can be passed into and out of the chamber. This is 

 guarded by a double port. There are also four tubular 

 openings through which pass telephone wires and wires 

 to an electromagnet and to the copper disc of a bicycle 

 ergometer, a cable from the beam of a balance placed 

 above the calorimeter, the entrance and exit tubes of the 

 radiator system of water-pipes, and a lever for adjusting 

 the position of shields covering the radiator system. .Ml 

 these apertures are sealed in various ingenious ways, but 

 none too securely. Doubtless practical experience will both 



