264 Dr. BT. H. Alcock. On the Negative Variation [Jan. 17, 



IV. FlLICALES. 



(a) Simplices. 



Marattiacese. 



Osmundaeese. 



Schizaeacese. 



Gieicheniacese. 



Matoninese. 



(b) Gradata?. 



Loxsomaceae. 



Hymenophyllacese. 



Cyatheaceae. 



Dicksoniese. 



Dennstaedtiinse. 



Hydropteridere (?). 



(e) Mixtae. 



Davalliese. 

 Lindsay ese. 



Pteridese, and other Polypodiacese. 

 V. Equisetales. 



Equisetacese. 

 Calamariese. 



" On the Negative Variation in the Nerves of Warm-blooded 

 Animals." By N. H. Alcock, M.D. Communicated by 

 A. D. Waller, M.D., F.K S. Eeceived January 17, — Read 

 February 12, 1903. 



(From the Physiological Laboratory, University of London, S.W.) 



Introduction. 



The negative variation in the nerves of warm-blooded animals has 

 already been the subject of several researches.* While the nerves are 

 still in connection with the tissues it has been the experience of most 

 observers that there is no difficulty in examining the negative variation, 



* Valentin, ' Pfliiger's Archiv,' vol. 1, p. 423 ; Fredericq, ' Du Bois Archiv,' 

 1880, p. 70; Hermann, * Physiologie,' vol. 2, p. 120 ; G-otch and Horsley, 'Phil. 

 Trans.,' " Croonian Lecture," 1891, p. 267 ; Macdonald and W. Reid, ' J. Physiol.,' 

 vol. 23, p. 100; Waller, 'Animal Electricity,' London, 1897; Boruttau, (a) 

 1 Centralbl. f . Physiologic,' vol. 12, p. 317, 1898, (b) ' Pfliiger's Archiv,' vol. 84, 

 p. 309, 1901. 



