112 Mr. K. Sassa and Prof. C. S. Sherrington. Myogram of the 



tibial crural and pedal muscles pass to the spinal cord vid the ipsilateral 

 dorsal roots of the 6th, 7th, 8th, and sometimes 9th post-thoracic spinal 

 nerves (5). Severance of these roots leaves still open for reflex play upon 

 the muscle several important afferent nerves of the limb, namely, internal 

 saphenous, femoralis, and external cutaneous. The two former will have 

 lost some of their afferent fibres, but will yet retain, as experience showed, 

 enough to evoke extensive reflexes. The motor nerve-fibres to tibialis are, 

 of course, untouched by the severance. 



Our procedure has been to cut, with full aseptic precautions and under 

 deep anaesthesia, the dorsal roots of the 6th, 7th, 8th, and 9th post-thoracic 

 nerves of one side, then a few days later to sever the cord aseptically at the 

 12th thoracic segment, and finally a few days later to decerebrate and proceed 

 in the same manner as before to the myographic observations of the reflex 

 and neuromyal contractions. As afferent nerves employed for evoking the 

 reflexes, our choice was, of course, limited to internal saphenous, femoralis, 

 and external cutaneous. By femoralis nerve is meant the whole anterior 

 crural trunk except internal saphenous. It includes, therefore, the afferent 

 nerve fibres from the quadriceps, extensor muscles, etc. Our observations 

 found that the break-shock reflexes elicited showed still (figs. 2 and 3) the 

 character of being, when the break-shock was of considerably above threshold 

 value, both longer and of greater crest-height than the maximal twitch elicited 

 by a similar stimulus applied to motor nerve itself. That the afferent arc of 

 tibialis antieus, etc., had been broken was guaranteed in each experiment in 

 several ways. For instance, by trial to obtain the proprioceptive reflex of the 

 muscle, this reflex proving to be inelieitable in each case, though easily 

 provocable in the contralateral limb. Also by post-mortem examination of 

 the spinal roots in the vertebral canal, which showed that the roots severed 

 had been those required : in two cases the posterior half of the 5 th root had 

 been cut as well. Also by inability to provoke by any means any reflexes 

 from the peroneal or popliteal nerves. The knee-jerk was also entirely 

 absent in three cases and extremely slight in two others. But as regards the 

 crest-height and duration of the break-shock reflex elieitable in tibialis 

 antieus, these remained often, when the stimulus was considerably above 

 threshold strength, superior to those of the maximal motor twitch-contraction. 

 We obtained, therefore, no support for the supposition that that superiority 

 was founded on combination of the break-shock reflex evoked from the 

 extrinsic afferent with a proprioceptive reflex iaitiated reflexly in the con- 

 tracting muscle itself. 



3. That the reflex contraction develops more than one single contraction- 

 wave (per fibre) is evidenced not only by the excess of crest-height above 



