664 



A MANUAL OF PHYSIOLOGY. 



In this way Helmholtz observed a rise of temperature of 

 0-14 to 0-18 C. in excised frogs' muscles when tetanized for 

 a couple of minutes. 



Heidenhain, with a very delicate pile, found a rise of 0-001 to 



0*005 C. 'for a single con- 

 traction of a frog's mus- 

 cle. On the assumption 

 that the pile had time to 

 take on the temperature 

 of the muscle before there 

 was any appreciable loss 

 of heat, this would be 

 equal to the production 

 by every gramme of mus- 

 cle of a thousandth to 

 five - thousandths of a 

 small calorie (p. 574) of 

 heat. From Pick's ob- 

 servations we may take 

 about three-thousandths 



B, two pairs, one inserted into the tissue b, the f 11 ra i orifi as . f v_ 

 other dipping into water in a beaker a. The 



temperature of the water may be adjusted so maximum production of 



that the galvanometer shows no deflection, a gramme of frog's niUS- 



FIG. 250. 

 A, a single copper-iron thermo-electric couple; 



The temperature of the tissue is then the same 

 as that of the water. 



cle in 

 tion. 



a single contrac- 



It is certain that when work is done by a muscle an equivalent 

 amount is subtracted from its sum-total of energy, and under 

 proper conditions this can be actually demonstrated by the deficiency 



As used for investigating heat- B B 



production in mammalian nerves ' j*) j^ ^ 



in situ. A, a piece of hard rubber 

 in the hook-shaped part of which 

 the fine platinum wire P is fixed, 

 and covered with insulating var- 

 nish ; c, c, thick copper wires 

 connected with P, fastened in 



grooves, and covered with paraffin. A R 



Above they end in contact with 

 the small binding posts, B^, 62. 

 B is a hard rubber sliding piece, 

 with a slot s. When B is in 

 position the screw, a, projects 

 through the slot. By a nut on 

 this screw B is fixed on A when 

 the nerve has been arranged in the 

 groove. A similar larger arrange- p' 



ment can be used for muscle. 



FIG. 251. ELECTRICAL-RESISTANCE 

 THERMOMETER (NATURAL SIZE). 



in the heat-production. This is done by means of a contrivance 

 called a work-adder. It consists of a wheel, the rotation of which 

 raises a weight attached to a cord wound round its axle. The 



