Myogram of the Flexor -rejlex evoked by a Single Break-shock. 109 



had been registered the nerve of the muscle was severed and its distal stump 

 stimulated for obtaining the motor twitch. For stimulation of the afferent 

 nerve the break-shock kathode was placed nearer to the spinal cord, for the 

 efferent nerve it was placed nearer to the muscle. 



Eemlts. 



It will be convenient to refer to the contraction evoked by the break-shock 

 applied to motor nerve as the neuromyal twitch. 



(1) Duration of Contraction. — The reflex myogram was almost always of 

 longer duration than the maximal twitch myogram. This was so even when 

 the height of the reflex myogram was considerably less than that of the 

 twitch (2). Often the excess in duration of the reflex contraction over the 

 maximal twitch was great ; the reflex contraction lasted sometimes even four or 

 five times as long as the twitch contraction. The reflex contractions evoked 

 from musculo-cutaneous nerve on the dorsum of the foot (skin) and from 

 internal saphenous were usually of longer duration than that evoked from 

 the popliteal, although their contraction height was less. In spite of general 

 similarity of form the reflex from the several nerves was found to present to 

 some extent features characteristic for the nerves severally. The prolonga- 

 tion of the reflex contraction lay chiefly in the prolonged subsidence of the 

 contraction after the crest of the myogram had been reached (fig. 1). 



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Fig. 1. — Break-shock reflexes (spinal preparation) of tibialis anticus ; upper line, internal 

 saphaneous nerve stimulated with secondary coil at 40 cm. from primary ; lower 

 line, popliteal nerve stimulated, coil at 15 cm., and, for comparison, a maximal 

 twitch contraction given by stimulating motor nerve (peroneal) with coil at 15 cm. 

 (break-shock). Time in 0-01". 



(2) Crest-height. — With the isometric myograph the height of the myogram 

 is an index of the degree of tension developed by the contraction. In the 

 reflex contractions the tension crest was reached relatively later after onset of 

 the contraction than in the neuromyal twitch. In most of our preparations 



