384 



Miss S. C. M. Sowton. Observations on the 



These experiments brought out very evidently what I am disposed to 

 regard as a principal difference between medullated and non-medullated 

 nerve. Whereas in medullated nerve successive effects diminish very 

 slightly or not at all, or actually increase (" staircase effect "), non- 

 medullated nerve always exhibits a comparatively rapid decrease of 

 successive effects. 



Figs. 4 and 5 illustrate this point. 



riG. 4. 



Medullated nevve (frog). Stimulation at l-minute intervals. 

 Fig. 5. 



A 



Non-medullated nerve (pike). Stimulation at l-minute intervals. 



The galvanometer used in these experiments was a Thomson, oi' 

 Muirhead's pattern, and was dead-beat. It was used with or without 

 photographic apparatus, the spot of light being in the last case reflected 

 on to a large transparent screen in the half-darkened room. 



The highly damped Thomson reacted too sloAvly for such fleeting 

 effects as the response of the nerve to single stimuli to be made visible, 

 but being dead-beat was most suitable for the study of positive after- 

 effect. 



With a normal olfactory nerve in its fresh state the positive after- 

 effect was never observed with this instrument, but a most striking 

 development of the phenomenon followed on subjecting the nerve to a 

 stream of carbon dioxide. The nerve was enclosed in a small moist 



