558 Prof. C. 8. Sherrington. On Reciprocal [Aug. 10, 
experiments accompanied regularly by inhibition of reflex contraction of 
the crossed vasto-crureus. This can be well seen in the double vasto-crureus 
preparation, the animal being inverted and the extension of knee maintained 
by vasto-crureus against the weight of the limb below the joint; the occur- 
rence of the “shortening reaction” in one vasto-crureus is then followed 
by the dropping of the opposite knee into flexion. This crossed inhibition, 
f 
Fig. 4, 
which obviously must be reflex, accompanies the elicitation of the “shortening 
reaction.” 
The evidence seems to warrant the conclusion that in the rigidity of the 
decerebrate vasto-crureus muscle the tonus of the reflex are which maintains 
the rigidity of the muscle is regulable in two opposite directions by reflex 
influences which can be started from the muscle itself. Regulation in one 
direction is shown by the “ lengthening reaction,” which is a reflex excited by 
