480 ELECTRO-PHYSIOLOGY .-HAI-. xn 



epithelial elements (the true sensory cells} are again the seat 

 of electromotivity , which is the more probable since it can 

 be shown that the changes produced by light are initiated in 

 these elements. According to Klihne and Steiner, however, this 

 is due less to primary photo-chemical processes occurring in the 

 external elements of the visual cells the alteration of the 

 hypothetical visual substance by light than to the con- 

 sequences of excitation of " the protoplasm contained in the 

 internal constituents of the visual cells, by the photo-chemical 

 products of disintegration." 



BIBLIOGRAPHY 



1. F. HOLMGKKN. Untersuchungen aus dem physiol. Inst. der Univ. Heidelberg. 



III. p. 278. 

 2. (a) DEVVAII and M'KENDRICK. Trans. Roy. Soc. of Edinburgh. XXVII. p. 



141. 

 (b) DEWAR. The Physiological Action of Light. Pro. Roy. Inst. 1876. 



3. KiJHNE and STEINER. Untersuchungen aus dem physiol. Inst. der Univ. 



Heidelberg. III. and IV. 



4. SIGM. FUCHS. Pfliiger's Arch. . LVI. 1894. p. 408. 



5. ENGELMANN. Beitriige zur Psychol. u. Physiol. der Sinnesorgane. H. v. 



Helmholtz zum 70. Geburtstag gewidmet. 1891. 

 ti. A. D. WALLER, (a) Points relating to the Weber-Fechner Law. (Retina, 



Muscle, Nerve.) Brain. 1895. 



(b) Action of Ether and Chloroform on Retinal Excitability. 

 Brain. 1896. p. 574. 



