Reflexes, etc., of Mammalian Nerve-muscle. 247 



appropriate strength applied direct to the distal stump of the cut motor nerve). 

 But the crest-height of the reflex contraction is attained later than that of 

 the maximal twitch even v^hen the height of the former is considerably less 

 than that of the latter. The decline of the reflex contraction is considerably 

 longer than that of the twitch. These differences accord with the considera- 

 tions admirably given by Forbes and Gregg (3) in their discussion of their 

 observations comparing the galvanometer records of the action current of the 

 break-shock flexion-reflex (decerebrate) with that of the directly stimulated 

 motor nerve. They pointed out that such difierences as those above are not 

 incompatible with the centrifugal impulses in the reflex, being, as for the 

 motor twitch, not more than one, i.e., not multiple, per nerve-fibre, since the 

 total volley in the reflex may very probably be less nearly synchronous, i.e., 

 may, though single per fibre, be distributed tlirough the constituent motor 

 fibres as a group during a somewhat longer period of time. 



Through a certain range of further increase of the break-shock stimulus the 

 same above-mentioned characters of the reflex contraction as compared with 

 maximal twitch continue to hold, but the crest-height of the reflex contraction 

 continually approaches more and more to that of the maximal-twitch and the 

 duration of the reflex contraction continues to be no less and usually still 

 further prolonged. Then, as the stimulus is further augmented, there is 

 reached a strength of stimulus at which the crest-height of the reflex 

 contractions equals and, with strengths of stimulus beyond that, exceeds, the 

 crest-height of the maximal twitch itself, while likewise the total duration of 

 the reflex contraction exceeds, usually very considerably, that of the maximal 

 twitch. 



The strength of stimulus at which the reflex contraction thus begins to 

 surpass the maximal twitch's crest-height is not necessarily great. Thus, in 

 the experiment from which fig. 1 is taken, the reflex contraction's crest-height 

 began to exceed that of the maximal motor-nerve twitch when the secondary 

 coil stood at 45 cm. from the primary, the maximal twitch compared with it 

 being sampled at 16 cm. of secondary's distance from primary. The stimulus 

 for the reflex was, therefore, very weak relatively to that used for the maximal 

 twitch, though the contraction evoked by the former was the greater. The 

 reflex contraction evoked by the coil at 40 cm. (fig. 1), still much weaker than 

 that used for the standard maximal twitch, exceeded the maximal twitch yet 

 more. With further increase of the stimulus the tension developed by the 

 reflex contraction may become considerably more than twice as great as that 

 developed by the maximal twitch ; and the duration of reflex contraction 

 twice or thrice or even four times that of the twitch. In the final steps of 

 increase of the stimulus, e.g., where the break-shock can be felt when the 



