FUNCTIONAL INERTIA AS LATENT PERIODS, &c. 41 



tetanic : in certain cases (frog and man) it can be 

 maintained for a relatively long time, half an hour. 

 In this state of fatigue we have a non-correspondence 

 between rate of stimulation and rate of response : 

 the ratio is of the order of 4 to i or 5 to I (frog's 

 gastrocnemius and flexor sublimis digitorum of 

 man) : functional inertia is here a factor. 



rUTJVVTJTJlJTJTJTJTJTJT^^ 



FIG. LI. Record of post-tetanic tremor'of human muscle (flexor sub- 

 limis digitorum) . Average periodicity^ to 6 per second : time in half- 

 seconds. 



Such a muscle as the frog's mylohyoid^which 

 is tetanised by ten impulses per second, i.e.., has 

 less affectability than the gastrocnemius, exhibits 

 a post-tetanic tremor of correspondingly slower 

 periodicity, viz., 2 a second ; but the ratio 10 to 2 

 is the same (5 to i). 



By affectability the gastrocnemius muscle keeps 

 pace with the increasing rate of stimulation from 

 i a second to 30 a second, when the limit is reached ; 

 thereafter any stimulation at 30 per second or higher, 

 gives rise to a tremor of no more than 4 to 6 a second 

 this is the expression of functional inertia through 

 a rhythm. 



