FUNCTIONAL INERTIA AS LATENT PERIODS, &c. 43 



or katabolites present amongst the biogens so reduce 

 their mobility that a state of much inertia and little 

 affectability is substituted for one where these 

 properties are present in the opposite relation- 

 ship. 



Neural fatigue at the motor end-plates coming 

 after prolonged muscular exertion sets a limit to the 

 further volitional stimulation of muscle ; the muscle- 

 fibres are still affectable to electric stimulation (i.e., 

 are not fully fatigued), and the brain itself is still 

 capable of emitting volitional impulses. The func- 

 tional inertia of the end-plates is the property under- 

 lying the physiological contrivance for preventing 

 the exhaustion of the still affectable muscular sub- 

 stance through the still possible volitional effort. 



The rhythmicality of such an organ as the heart is 

 dependent to a very great extent upon the inertial 

 property. The origination of a rhythm may be due 

 to affectability, but in many cases the rhythm is 

 maintained through functional inertia. Thus the 

 avascular, isolated, non-fed heart " beats " for a 

 longer or shorter time according as it has more or 

 less of the inertial property. Mr. Morrison writing 

 on "Tachycardia"* thus expresses himself: "the 

 heart appears to revel in the foetal tic-tac of eman- 

 cipated visceral rhythmicality." 



"Emancipated" from what? from the heart's 

 existing environment : this emancipation is now- 

 correspondence with environment, which is, as we 



* Morrison, " The Disorders of Visceral Motion." Lecture VI, 



Edinburgh Medical Journal, p. 106. 



