50 



ANIMAL MECHANISM. 



animal furnish manifestations of dynamic electricity. Mat- 

 teucci has discovered the manner in which the muscular 

 current is usually produced. Du Bois Reymond has added 

 much to our knowledge of this current, of its intensity, and 

 of its direction in every part of a muscle. Treatises on phy- 

 siology give copious details of experiments relaitive to nervous 

 and muscular electric currents. This study has been the 

 more eagerly pursued because the proximate cause of the 

 function of the nerves and muscles was expected to be found 

 in these electric phenomena. 



The most interesting fact connected with muscular elec- 

 tricity, with respect to the transformation of force, appears to 

 be the disappearance of the electrical state of a muscle at the 

 moment when it contracts, or when it is tetanized. It appears 

 then that the chemical actions of which the muscles are the 

 seat, are entirely employed in the production of heat and 

 motion. 



To observe these phenomena, we must make use of a very 

 sensitive galvanometer. Suppose a muscle connected with one 

 of these instruments ; it gives its currents, and deflects the 

 magnetic needle a certain number of degrees. When this de- 

 viation has been effected, and the needle has become stationary 

 in its new position, it is only necessary to produce tetanus in 

 the muscle, and immediately the needle retrogrades towards 

 zero. This is what Du Bois Beymond calls the negative varia- 

 tion of the muscular current. The same phenomenon is 

 observed in the voluntary contraction of the muscles. 



The interpretation of the negative variation is very im- 

 portant. Du Bois Beymond having remarked, that for a 

 single muscular shock no deflection of the needle from zero is 

 obtained, concluded that this is on account of the short dura- 

 tion of the electrical disturbance accompanying a shock. In 

 tetanus, on the contrary, a series of modifications in the 

 electrical condition of the muscle correspond to the series of 

 shocks produced — their accumulated influence deflects the 

 magnetic needle. 



This phenomenon is familiar to physicists. It is known 

 that the needle of a galvanometer subjected to a frequently- 

 interrupted current, takes a fixed position intermediate be- 



t 



