286 Prof. C. 8. Sherrington. [ Apr. 17, 
This exception apart, the striking invariability of the reflex reactions from the 
various skin-points and nerve-twigs, together with the correspondences 
mentioned in Section I, allows an inference that the individual afferent 
Fig. 8. 
QRS 
BHR 
Sy 
es 
SS 
“ 
SWS 
> 
<2 
Pesos 
FS O35eeS 


EO 
See 
RSS 

x . 
SOOSS 


BSS 
Se S> 
S ROSS > 
< 
Ss 
eee! 
WS 
See 
> 

om \ 
Fic. 8.—Diagram indicating connections and actions of two afferent spinal root-cells, a 
and a’, in regard to their reflex influence on the extensor and flexor muscles of the 
two knees. a, root-cell afferent from skin below knee; a’, root-cell afferent from 
flexor muscle of knee, 7.e., in hamstring nerve; ¢ and e’, efferent neurones to the 
extensor muscles of the knee, left and right ; 5 and 0, efferent neurones to the flexor 
muscles; E and E’, extensor muscles ; F and F’, flexor muscles. The “ schalt-zellen ” 
(v. Monakow) probable between the afferent and efferent root-cells are for simplicity 
omitted. The sign + indicates that at the synapse which it marks the afferent. 
fibre a (and a’) excites the motor neurone to discharging activity, whereas the sign 
— indicates that at the synapse which it marks the afferent fibre a (and a’) inhibits 
the discharging activity of the motor neurones. The effect of strychnine and of 
tetanus toxin is to convert the minus sign into plus sign. 
nerve-fibres from the receptive-field of the reflex each divide in the spinal 
cord into end-branches (¢.g., collaterals), one set of which, when the nerve- 
