CHAPTER XXXV 



MECHANICAL RESPONSE OF NERVE 



Current assumption of non-motility of nerve Shortcomings of galvanometric 

 modes of detecting excitation Mechanical response to continuous electric 

 shocks Optical Kunchangraph Effect of ammonia on the mechanical 

 response of nerve Effect of morphia Action of alcohol Of chloroform- 

 Abnormal positive or expansive response converted into normal contractile 

 through diphasic, after tetanisation Similar effects in mechanical response 

 of vegetable nerve Mechanical response due to transmitted effects of 

 stimulation Determination of velocity of transmission Indeterminateness 

 of velocity in isolated nerve Kunchangraphic records on smoked glass- 

 Oscillating recorder Mechanical response of afferent nerve Record of 

 mechanical response of nerve due to transmitted stimulation, in gecko 

 Fatigue of conductivity Conversion of normal contractile response into 

 abnormal expansive, through diphasic, due to fatigue. 



I HAVE already referred to the distinctions which are com- 

 monly insisted on, as between the reactions of different 

 animal tissues. Certain of these are regarded as motile 

 and others as non- motile. From an evolutionary point of 

 view, however, it is difficult to conceive of such a hard-and- 

 fast distinction. It would be easier, believing in continuity 

 to suppose that a certain responsive reaction, characteristic 

 of the simplest living substance, had become accentuated 

 in some tissues, and not so accentuated in others, according 

 to their different functional requirements. Thus the belief 

 held so implicitly by physiologists that nerves exhibit no 

 motile response whatsoever l becomes questionable, and is 

 seen to require investigation. After submitting it to this, 

 moreover, one finds it difficult to understand how such an 



1 ' Nerves are irritable ; when they are stimulated, a change is produced in 

 them ; this change is propagated along the nerve, and is called a nervous impulse ; 

 there is no change of form in the nerve visible to the highest powers of the 

 microscope.' (Kirke's Handbook of Physiology ', I5th edition, p. 105.) 



