MUSCULAR CONTRACTION 



13 



attribute of the muscular mechanism, but is a phenomenon 

 shared by other excitable tissues. It has been the subject of 

 extensive research partly because of its practical application 

 to the diagnosis of heart disease (electrocardiography), partly 

 because it provides a very delicate means of detecting the 

 existence of an excitatory process, where mechanical appUances 

 fail, and to some extent because it has been customary in the 

 past to seek for an explanation of colloidal behaviour, and 

 therefore the processes which occur in the living organism, in 



Fig. 3. — Time relations of the electrical variation in the isometric 

 response to two successive stimuli (after Fulton). 



Responses of the intact gastrocnemius of a decerebrate frog at 16 5°. 

 Time indicated above, o"02 sec. The horizontal shadows from above 

 downwards are : the signal denoting the moment of the second stimulus 

 (make) ; the myograph ; the string of the galvanometer ; signal for the 

 first stimulus (break) ; line of zero tension, 29 mm. movement of the 

 myograph vertically being equal to 500 gms. tension. String tension 5 mm. 

 per m. V. , the magnification being 285. Stimuli delivered to the cut nerve, 

 the cathode being at a point I'g cm. from the entry of the nerve into the 

 muscle; stimuli just-maximal induction shocks. Initial tension 90 gms. 

 Frequency of the myograph 460 per sec. 



terms of electrical phenomena rather than the stoichiometrical 

 relations which form the subject-matter of traditional 

 chemistry. 



There is Httle doubt that the demarcation current arises 

 from the distribution of electrolytes in the muscle system ; its 

 relation to temperature, according to the work of Bernstein, 

 follows the thermodynamical relation which applies to the 



