1909.] 



Innervation of Antagonistic Muscles. 



257 



(fig. 8). In other words, a balance between the reflex inhibition and the 

 reflex excitation which tonus expresses is never attained. 



This state of tonus appears due to a natural stimulation of mild steady 

 quality, and in decerebrate rigidity it is, as has been shown, autogenous 

 in the sense that its afferent path is constituted by proprioceptive nerve- 



Fig. 8. — Vastocrureus preparation in Decerebrate Rigidity. Reflex inhibition is pro- 

 duced by stimulation of the central end of the severed ipselateral peroneal nerve 

 below knee, the stimulus being a series of slowly repeated break induction shocks, 

 shown by the signal lines SA and SB. Time is marked (TA, TB) in fifths of 

 seconds. In observation A the break-induced currents were more intense (100 units 

 of Kronecker scale) than in observation B (20 units of Kronecker scale). Cat, decere- 

 brate preparation. In both the observations the relaxation of the muscle proceeds 

 to the full resting length of the muscle, but in observation A the fully relaxed 

 condition is obtained speedily in the course of nine repetitions of the stimulus ; 

 whereas in observation B the same degree of relaxation is reached only gradually in 

 the course of eighty-six repetitions of the (weaker) stimulus. The signal line at the 

 foot of the figure marks the duration of the stimulation in observation B. 



fibres arising in the muscle itself.* This autogenous tonus no artificial 

 stimulus such as we apply to afferent channels experimentally for evoking 

 reflexes has as yet succeeded in giving. The failure to exactly balance the 

 natural reflex excitation which maintains this tonus by any artificial 



* Sherrington, 'Quart. Journ. of Expt. Physiol.,' vol. 2, p. 109. 



