76 rHYSIOLOGY UF MUSCLES AND NERVES. 



In order to form some conception of the amount of 

 warmth thus generated, we will assume that the specific 

 warmth of muscle is the same as that of water. As the 

 greater part of muscle consists of water,' this assumption 

 cannot be far wrong. By the specific warmth of a sub- 

 stance is meant that amount of warmth which is neces- 

 sary to warm one gramme of the substance exactly one 

 degree, the amount necessary in the case of water being 

 regarded as the unit. Therefore about one unit of 

 warmth is requisite to warm one gramme of muscle 

 substance one degree. According to our assumption, in 

 each gramme of muscle substance at least '15 of a unit 

 of warmth is generated. Now it is known that each 

 unit of warmth is equivalent to 424 units of work, that 

 is to say, when warmth is transformed into mechanical 

 work, 424 grammes can be raised one metre by one 

 unit of warmth. If, therefore, no warmth were set free 

 from the muscle during tetanus, but if it were trans- 

 formed into work, each gramme of muscle substance 

 would be able to raise 424-^0*15 gramme to the height 

 of one metre. This amount, therefore, represents the 

 minimum of that which is accomplished as ' internal 

 work ' in the muscle during tetanus. 



By soldering rods or strips of two metals alternately 

 on to each other so that all the points soldered are 

 arranged in two planes, differences in temperature much 

 more minute than those which occur during tetanus 

 may be measured. Such an apparatus is called a thermo- 

 pile. Heidenhain had one of these made of rods of 



' According to a recent statement of Dr. Adamkiewicz, the spe- 

 cific warmth of muscle is even greater than that of water, though it 

 had previously been sssumed that the specific warmth of water is 

 greater than that of any other known substance, with the excep- 

 tion of hydrogen. 



