49,3 



Croonian Lecture : The Process of Excitation in Nerve and 

 Muscle. 

 By Keith Lucas. 



(Communicated by Sir John Bradford, Sec. B.S. Eeceived June 6, — Lecture 

 delivered June 6, 1912.) 



To physiologists working half a century ago it must have seemed that there 

 was scarcely a problem of their science more hopeful of solution than that of 

 the physico-chemical nature of the nervous impulse. Helmholtz had recently 

 measured the rate at which the impulse is propagated along a nerve. 

 Du Bois Pieymond's researches had placed the .study of animal electricity on a 

 scientific basis, and there was just commencing that work of Bernstein which 

 coupled the two phenomena by mapping out the time-relations of the electric 

 change which sweeps along an active nerve, and showing how this change 

 keeps time with the nervous impulse. 



But the problem is still unsolved ; indeed, the progress towards solution 

 was for a long time of such a nature that physiologists were able 10 years ago 

 to write such words as these : " After decades of work by so many distinguished 

 investigators we are as far as ever from the understanding of the intimate 

 nature of nervous excitation,"* ; or, again : " In recent times voices have been 

 heard belittling the scientific value of electrophysiologyf " ; or, in the more 

 picturesque words of v. UexkullJ : " For whole decades the frog's leg has been 

 investigated without being crippled by the shrewdest heads and the most 

 talented experimenters." 



I do not come before you to-day with any new solution of this problem. 

 Nor shall I even attempt to criticise those many solutions which physiologists 

 have offered from time to time. My aim will be more elementary than that ; 

 it will be to enquire into that fundamental analysis of the biological phenomena 

 concerned, which must precede any formulation of physico-chemical hypotheses, 

 and to see how far that analysis can guide us towards the building of our 

 hypothesis on a sure foundation. To each investigator of the phenomena of 

 the excitable tissues there must stand out pre-eminently some aspect of past 

 work which will seem to account for the slow measure of progress. By some 

 of those writers whom I have quoted the cause of failure was located in the 

 too artificial handling of the problem as one of physics rather than of 



* Biedermann, 'Ergeb. d. Physiol.,' 1903, vol. 2, Part 2, p. 132. 

 + Loeb, 'Arch. f. d. ges. Physiol.,' 1902, vol. 91, p. 248. 



\ v. Uexkull, 'Leitfaden in d. Stud. d. Exp. Biologie,' Wiesbaden, 1905, p. 5. 



