Note on thc after-discliar^t- of reflcx unlri-. ■. , 



contracting muscle itsell. The muscle contains within it Ihe receptive 

 endings of its own manifold alVerent nerve-fibres. Ihe active contrac- 

 tion of the muscle may form a stimulus to tlie muscle-spindles, tendon- 

 organs, etc., w liich belong to its own proprioceptive afferent nerve. Ihis 

 stimulus may provoke a reflex contraction of the muscle itself, which 

 adds an additional reflex to the reflex already excited, and may continué 

 when the primary stimulation has ceased. It w ould then appear as an 

 appendix to the primary reflex, as in fact a post-stimulation after-dischar- 

 ge from the centre, and by the miograph, as a post-stimulatory continua- 

 tion of the contraction. Such an explanation, however, will not explain 

 fully the reflex after discharge because it is still obtainable after the affe- 

 rent nerve-fibres froni the muscles have been severed; it is difficult to de- 

 cide whether it is then as extensive as it was before the cutting of the 

 proprioceptive nerves. 



There seems, therefore, to be in the reflex centre some mechanism 

 Mhich, when excited by the arrival of a centripetal impulse from the afie- 

 rent nerves, develops a state of excitement longer lasting than the cen- 

 tripetal impulse itself. 1 he morphological structure in the centre which 

 is the seat of this longer-lasting state of excitement may be the perika- 

 ryon of some constituent neurone of the reflex centre. The fact that the 

 perikaryon, as shown long ago by Ramón y Cajal and otiiers in notable 

 instances, lies aside from the main line of conduction between dendrite 

 and axone, appears to me to argüe against the suggestion that theperika- 

 ryon is answerable for the reflex afterdischarge írom the centre. Ano- 

 tlier possibility is that the synapse, the place of contact between the axo- 

 ne-terminal of one neurone and the surface of the dendrite or perikarion 

 of the next neurone in the reflex chain is the structure at which the excit- 

 ed state persists in reflex action. For instance, if the point of contact 

 of the terminal plaque of an axone applied to the surface of a dendrite or 

 the perikaryon of a moto-neurone exhibited in result of a nerve-impulse 

 received via the axone, a state of excitement which lasted longer than the 

 nervous impulse, it would presumably produce in the moto-neurone not 

 one nervous impulse, but a series. Ihe moto-neurone is a cell which 

 can reply only rhythmically. The result of the relatively long dura- 

 tion of the state of excitement at the inter-neuronic synapse would 

 be a rhyth mic discharge of centrifugal impulses along the eflerent 

 nerve-fibres. 



