RESPONSE OF NERVE 



725 



The experiments which have just been described were carried 

 out on the efferent gastrocnemius of frog and gecko. With 

 the afferent optical nerves of certain fishes I obtained 

 mechanical responses which were exactly the same as these 

 (figs. 324, 402). That is to say, in a sub-tonic condition the 

 optic nerve gave the abnormal positive or expansive re- 

 sponse, and this was subsequently converted into the normal 

 contractile responses, through an intermediate diphasic. 



The mechanical response of nerve just described, may be 

 recorded either photographically, by a reflected spot of light, 

 or directly on a smoked-glass surface by means of a writing- 

 point. The difficulties due to friction in the latter case are 

 obviated by the use of the Oscillating Recorder. By means, 

 however, of a battery of levers, and using the optical method 

 of record, it is possible to have a magnification by the 

 Kunchangraph of one hundred thousand times or more, the 

 sensitiveness of the record being correspondingly enhanced. 

 By this means many new phenomena may be brought under 

 observation, one of these being the multiple response induced 

 by strong stimulus in nerve. It is known, again, that nerve 

 becomes highly excitable during the setting-in of ' drying,' and 

 under these conditions, in a nerve-and-muscle preparation, 

 repeated mechanical spasms are exhibited by the attached 

 muscle. In taking the mechanical record of nerve, it is found 

 that the substitution of dry for moist air at once induces a 

 visible contraction. Now this state of partial contraction, 

 bringing the nerve, as it does, into condition B, we know to 

 be significant of enhanced excitability. If the drying of the 

 nerve be now allowed to continue, it is found that there is 

 induced a series of multiple responses (fig. 326). And the 

 multiple spasms seen during drying in the muscle of a 

 muscle-and-nerve preparation undoubtedly have, as one of 

 their factors, these multiple excitations thus demonstrated 

 to take place in the nerve. 



With the highly magnifying Kunchangraph, again, the 

 individual effect of a single shock is demonstrated with the 

 greatest clearness. Under rapidly succeeding tetanising 



