ELECTRO-PHYSIOLOGY 



CHAr. 



40 niin. 



indicated, as much the 

 effect of a " down " 

 change in living matter, 

 caused by the preponder- 

 ance of D over A pro- 

 cesses, as is the gradual 

 death of a muscle separ- 

 ated from, the organism, 

 or deprived of circulation. 

 We should therefore ex- 

 pect the changes which 

 occur in the twitch (or 

 contraction) in both cases 

 to agree in all essential 

 points. Decrease in 

 magnitude of contraction 

 (height of twitch), and 

 elongation (extension) of 

 the curve, appear in 

 either case as distinct- 

 ive features. This is 

 very apparent in the 

 pulsations of the excised 

 mammalian heart (55), 

 when the fall of tem- 

 perature (infra) plays an 

 important part (Fig. 44). 

 Although the condi- 

 tion of muscular fatigue 

 may thus be referred 

 mainly to a preponder- 

 ance of the D- process 

 over the simultaneously 

 occurring A-process, i.e. 

 to a diminution of the 

 store of decomposable 

 matters, or of chemical 

 tension, we must not 

 neglect the other and 

 important factor which 



FIG. 44. Contractions of excised Rabbit's heart. 

 (Waller and Reid.) 



