OF ELECTRICITY IN ANIMALS. 49 



which, lasts only for some hundred ths of a second, represents 

 the time of application of eacli element of the force of the 

 muscle. At each new wave, there would be produced a true 

 sJwck if the elasticity of the fibre did not extinguish this 

 abruptness, and transform these jerky little contractions into a 

 gradual increase of tension whicli constitutes the prolonged 

 effort of the muscle. 



A 7iiotor only works on the double condition of developing 

 an effort, and accomplishing a motion. Thus a muscle \vhicli 

 contracts, performs no external work, except while it is con- 

 tracting; as soon as it has reached the limit of its contraction, 

 it ceases to work, whatever may be the effort whicli it 

 develops. When we sustain a weight after having 1 lifted it, 

 the act of sustainment does not constitute work. 



But, in these conditions, to maintain the elastic force of the 

 muscle, the same acts are produced in its interior as during 

 the work; the muscular waves succeed each other at short 

 intervals, and heat is disengaged by chemical action. No\v, 

 this heat, whicli cannot transform itself into action, ought 

 to remain in the muscle, and heat it strongly. This is pre- 

 cisely what we observe, so that in the malady called tetanus, 

 whicli consists of a permanent tension of the muscles, it 

 is ascertained that heat is produced with an exaggerated 

 intensity, the temperature of the entire body rising several 

 degrees. 



o 



CHAPTER VI. 



OF ELECTKICITY IN ANIMALS. 



Electricity is produced in almost all organised tissues Electric currents. 

 of the muscles and the nerves Discharges of electric fishes ; old 

 theories ; demonstration of the electric nature of this phenomenon 

 Analogies between the discharge of electrical apparatus and the shock 

 of a muscle Electric tetanus Eapidity of the nervous agent ill the 

 electrical nerves of the torpedo ; duration of its discharge. 



MOST of the animal or vegetable tissues are the seat of 

 chemical actions, whence result an incessant disengagement 

 of electricity. In this way, the nerves and muscles of an 



