Literary Notices. 375 



electrical i iirrent passim.'' thr<)iiL''li the eyes. A variation of the linien 

 of the hght stiiniihis was pnxhu ed neither when the current flowed 

 from the layer of nerve fibers to the layer of rods and cones, nor when 

 the current (lowed in the opposite direction. 



Finally the author tested the effe( t of lonir continued pressure 

 upon the visual process of adaptation for darkness. A threshold value 

 was taken, (1) after j;o minutes in the dark room, (2) after wearing, for 

 30 minutes a liiiht-tiiiiit handatic wiiich exerted no pressure, and (3) 

 aftt'r wearing; a pressure I»an(la<j;e for 30 minutes All three cases gave 

 exactly the same threshold value. j. 1;. w. 



Abelsdorff, G. and Nagel, W. A. Ufhcrdic Waliniclumni^ dcr Hhithcwegung 

 ill (Icii N(t/liMiiik.i|)ill;Ufii. Zeit. f. Psy. u. PItvs. d. Sinnesorgane, Bd. 34, 



IM'- ^'M-30o, 1.104. 



If one glances at the blue sky, one sees, as is well known, numer- 

 ous small i^littering particles moving in tortuous pathways across the 

 field of view. The |iarti< U's are in constant motion, and since they 

 never pass the point of clfarest vision, it is impossible clearly to make 

 out their torm. I he phenomenon is in some way connected with the 

 circulation of the lilood in the retina. If one presses lightly with the 

 finger against the eyeball, the regular and uniform movement of the 

 particles changes to one of a pulsating c haracter, while a stronger 

 pressure brings the parti( le-^ almost to a standstill. Then after the re- 

 lease of the pressure the particles hasten ac:ross the field of view even 

 more ra|)idlv than bctore. That the phenomenon is not produced by 

 the mt'< hanir d stimulation of the elemciUs sensitive to light by the 

 blood c ells whi( h c irculate in the capillaries is proved by the fiict that 

 it is wholl\- hu king in darkness and weak lights, and even in stroni;- 

 lights the phenomenon can be seen only when the stimulating lights 

 possess wave lengths lying within delinite boundaries. 



i'>oth Ivii 11 and Rooii ha\e mentioned this jjlicnomenon and re- 

 marked that it ( an be' be^t observed with the aid (d' blue glass. The 

 present investigators t'lnding, however, that the movement of the par- 

 tic les cannot be seen with the aid ot anv and every blue ligiit jointly 

 undertook to mike a more thorough investigation of the conditions 

 under whic h this iihenomenon ajipears. 



AccordiuL: to their view there are two possible wavs of explaining 

 tile phenomenon : it mav be a shadow phenomenon, similar to that 

 of the vein-t"iunre> of W kki\ii , caused bv the absorption td" certain 

 Hiiht ravs bv the blood lorpusc les ; or it mav be a jjlienomenon ot 

 liuht refrac tioii. since eoiiceivablv the red and white corpuscles, acting 

 as lenses, nii-ht fo( iis the li'^ht on the seiisitiv e laver or the retina. Tlie 



