298 Reflex Rhythm Induced by Excitation and Inhibition. 



up or potential; when (A) becomes greater than (B) the accumulated energy- 

 is released and becomes kinetic. The force (B) need not be constant, but if 

 it increases during the increase of (A), its rate of increase must fall off below 

 the rate of increase of (A) before the release can occur. The crucial point is 

 this : that when once the release of energy begins it proceeds until more 

 energy is released than is represented by the excess of (A) over (B). The 

 condition which determines this may be figured as a sort of momentum of 

 discharge, although it may not involve inertia in any strict sense of the 

 word. 



I believe this consideration is important in connection with vital rhythmic 

 activities. Yerworn* has described the series of events which condition 

 intermittent strychnine convulsions. He states that with a violent discharge 

 there is a fall of irritability to the zero point. But he does not emphasise 

 the particular condition which makes the tissue discharge intermittently 

 instead of continuously, namely, that the discharge once started does not 

 stop when the excess of tension has been relieved, but proceeds to com- 

 pletion. To develop rhythm of discharge there must be an approximation 

 to the " all or none law " of the heart beat. A group of " biogen molecules " 

 (Verworn), combining with oxygen and giving off cleavage products in 

 accordance only with the law of mass action, would yield a continuous 

 response to a continuous stimulus. 



I believe these considerations have a general bearing on the oscillations 

 shown in the figures. We may suppose that there is in any given case 

 a degree of activity which would be the resultant of the opposed tendencies 

 if equilibrium ever occurred. If these tendencies were in stable equilibrium 

 at this neutral point any oscillations occurring at the outset would diminish 

 and disappear as in the case of a pendulum coming to rest. But the fact 

 that the oscillations generally do not diminish, and sometimes increase, as in 

 fig. 2, shows that at the imaginary neutral point the tendencies are in 

 unstable equilibrium. Some property of the discharge carries it past this 

 neutral point and prevents the establishment of an equilibrium in which the 

 discharge would steadily consume the excitatory tension. There seems to be 

 in the discharge of reflex impulses, and perhaps in all vital activities, some 

 phenomenon akin to the " all or none law " with its refractory period, which 

 makes for intermittence of response. 



* 'Arch, fur Anat. u. Physiol.,' 1900, p. 174. 



