MUSCULAR CONTRACTION. 475 



well-marked spasms under ten excitations per second, a 

 more complete fusion of the different acts with twenty per 

 second, and a complete fusion, or tetanus, with twenty-seven 

 per second. When the contraction had become continuous 

 that was an elevation in the line, showing increased power, 

 as the excitations became more and more frequent. 1 



This is precisely the kind of contraction that occurs in 

 the physiological action of muscles. Although the ner- 

 vous force is not by any means identical with electricity, 

 either the interrupted galvanic current or a series of statical 

 discharges is capable of producing a muscular action very 

 like that which is involved in voluntary movements. The 

 observations of Marey, showing that the intensity of what 

 he terms artificial tetanic contraction is in proportion to 

 the rapidity with which the electric discharges succeed each 

 other, are exceedingly interesting in their practical applica- 

 tions ; and an important question at once arises regarding 

 the nervous force that excites voluntary motion. Is this a 

 series of discharges, as it were, producing a power of mus- 

 cular contraction in exact proportion to their rapidity ? In 

 view of the experiments just cited, this theory is very prob- 

 able ; and it is certain that a rapid succession of electric dis- 

 charges almost exactly simulates the normal action. That 

 vibrations, more or less regular, actually occur in muscular 

 contraction has been settled beyond a doubt by the re- 

 searches of Wollaston, Haughton, and more lately by Helm- 

 lioltz, the latter having recognized a musical tone in con- 

 tracting muscles, exactly corresponding with the number of 

 impressions per second made upon the nerve. He further 

 devised an ingenious method of recognizing the tone, by fill- 

 ing the ears with wax and contracting the temporal and 

 masseter muscles. Marey has found, in repeating this 

 experiment, that the tone may be changed by modifying the 

 intensity of the muscular action. With the jaws feebly con- 

 tracted, a grave sound is produced, and this can be raised 



1 MAREY, op. cit., p. 373, et seq 



