ELECTRICAL PHENOMENA OF NERVE 189 



The latter varies for different muscles as follows : M. deltoideus, 

 58 to 62; M. gastrocnemius, 42 to 44; M. masseter, 88 to 100, 

 etc. These figures represent the rate of discharge of nerve 

 impulses per second by the nerve cells of the spinal and cranial 

 motor nuclei. 



The energy liberated by muscle appears in mechanical, 

 thermal, and electrical form. The last is so small that in quan- 

 titative determinations it is negligible. Only one-fourth to 

 one-twentieth of the chemical energy liberated by the muscle 

 appears as mechanical energy. The work done by a muscle 

 depends upon its nature and condition, the stimulus applied, 

 and the mechanical conditions under which the work is done. 

 Work is calculated by multiplying the load into the height to 

 which it is lifted. The absolute muscular force of a muscle is 

 the maximum weight that it can lift per unit cross-section. 

 This for the frog is 3 kilograms per square centimeter. The 

 heat liberated by active tissue is measured by a thermopile or 

 a bolometer. The first consists of a certain number of junctions 

 of two dissimilar metals like antimony and bismuth, which 

 develop an electrical current whenever any two of the junc- 

 tions are at a different temperature. The action of a bolometer 

 depends upon the fact that the electrical resistance of a wire 

 varies with the temperature. An isolated muscle has by means 

 of these instruments been found to produce by a single contrac- 

 tion, per gram of muscle substance, sufficient heat to raise 3 

 milligrams of water 1 degree centigrade. 



Electrical Phenomena of Nerve. Electrical energy is exhibited 

 by many forms of living matter. In order to study its mani- 

 festations in muscle and nerve it is necessary to take special 

 precautions by using non-polarizable electrodes in place of the 

 ordinary metal contacts. This for the following reason: 



It is now assumed generally that the molecules of any solu- 

 tion which is a conductor of electricity are in a state of dissocia- 

 tion i. e., the molecules are divided into two or more parts, 

 called ions. Thus sodium chloride in water becomes separated 

 into a sodium ion charged positively with electricity and into a 

 chlorine ion charged negatively. The passage of a galvanic cur- 

 rent through such a solution is accomplished by means of the ions, 

 and gives rise to electrolytic phenomena consisting of a migra- 

 tion of the positively charged ions or kations to the negative 



