ANIMAL ELECTRICITY. LECTURE IV. 99 



parativc magnitudes of anelectrotonic and katelectrotonic 

 effects in tlie different classes of nerves, viz., A. much greater 

 than K. in non-medullated nerves, A. greater than K. in 

 mechillated nerves of cold-blooded animals, A. equal to K. in 

 medullated nerves of warm-blooded animals. 



But I am still in doubt concerning the " physiological " 

 nature of the extrapolar A. and K. currents of isolated 

 mammalian nerve, nor do I yet know whether the absence 

 of '* negative variation " on such nerves is in any way con- 

 nected with the equality of these currents. 



REFERENCES. 



" Polar effects " were first fully described by Pfluger in his 

 " Untersuchungen uber die Physiologie des Electrotonus." 

 Berlin, 1859. 



The polar effects on Man are described by Waller and de 

 Watteville in the Phil. Trans. R. S. for 1882. (Influence 

 of Galvanic Current on the Excitability of Motor Nerves 

 of Man.) 



Polarisable core-models were first systematically investi- 

 gated by Hermann {Pfliiger's Archiv, vols, v., vi., vii., 

 1872-3. Handbuch, vol. ii., p. 174). They have recently 

 been still more closely studied by Boruttau. Pfliiger's 

 Archiv, 1894-6. 



These three topics are briefly summarised in my " Intro- 

 duction to Human Physiology," 3rd Ed., pp. 364, 2>^6, 370. 



Internal polarisation first alluded to by du Bois-Reymond in 

 the " Thierische Elektricitat " in 1849, and again in 1883 



