THE LIBERATION OF ENERGY 167 



fish and the glow-worm and fireflies. Even 

 in the human body there are also electrical 

 phenomena. Every contraction of a muscle, 

 the secretion of a gland, and probably also 

 nutritional changes in the tissues, are asso- 

 ciated with electrical phenomena, which may 

 be demonstrated by a sensitive galvanometer 

 and suitable methods. It can be shown that 

 antecedent to every muscular contraction 

 there is generated a change in the electrical 

 condition of the muscle. Whether this elec- 

 trical state is an expression of the chemical 

 changes in the muscle, on which motion and 

 heat depend, or whether it is an isolated physi- 

 cal phenomenon, it is difficult to say. Even 

 the heart beats are associated with electrical 

 phenomena. Living nerves also show elec- 

 trical changes similar in kind to those found 

 in muscle. It is significant that the electrical 

 organs of fishes are modifications of muscles 

 or glands. Thus the electrical organs of the 

 Torpedo occellata (of the Mediterranean), of 

 the Gymnotus electricus or electric eel (of the 

 Orinoco), and of the skates (Raid) are all 

 modifications of muscle, while that of the 



