156 STUDIES IN ELECTRO-PHYSIOLOGY: 



Reading on, we are told that " if the muscles of a frog 

 (Du Bois-Reymond) or tortoise (Briicke) be kept in a cool 

 place, they may remain excitable for ten days, while the 

 muscles of warm-blooded animals cease to be excitable 

 after one and a half to two and a half hours. ... A 

 muscle when stimulated directly, always remains excitable 

 for a longer time when its motor nerve is already dead." 



I have tested toads and tortoises galvanometrically in 

 years gone by, and have been astonished at their super- 

 abundant nerve energy as compared with that of man. 

 Moreover, their insulation, absolute and internal, is such 

 that they can withstand extremes of temperature and exist 

 without food for incredible periods of time. To compare 

 the muscle of a tortoise with that of a warm-blooded animal 

 is to compare an ivy leaf with a deciduous leaf. By 

 reason of its higher insulation the former will live (i.e., 

 remain excitable) for months, whereas a horse-chestnut 

 leaf will perish, under the same conditions, in a few days. 

 It is, to my mind, purely a question of insulation. Suppos- 

 ing there to be any resistance remaining in Krause's 

 membranes and any conductivity in the clear substance, 

 condenser-action would continue- in some degree ; but in 

 the dead muscular fibres of warm-blooded animals there 

 would, I should think, be rapid diffusion, short-circuit, and 

 consequent cessation of condenser-action. 



The statement that " a muscle when stimulated directly 

 always remains excitable for a longer time when its motor 

 nerve is already dead " is almost elementary. Part of the 

 sensory nerve of an apple is its stalk. When the apple is 

 ripe, and it falls, Nature seals the end of the stalk with a 

 resinous insulating substance. Granting, then, the sar- 

 comeres to be structurally intact, a dead motor nerve 

 would be equivalent to the sealed sensory nerve-ending of 

 the apple. On the other hand, if the motor nerve of the 

 muscle was maintained in a moist condition it would not 



