Literary Notices. 173 



however, reconcilable with Hering's general theory if specific brightness is dropped. 

 They also may be made to fit Helmholtz's theory if one supposes, following sug- 

 gestions of FiCK and Konig, that total color-blindness is not due to the absence of 

 all three components but rather to a modification in their relative excitability so 

 that their curves coincide. The resulting curve would then take the course of that 

 for the brightness values in "day vision." 



R. P. ANGIER. 



Piper, H. Ueber die Functionen der Stabchen und Zapfen und iiber die physiologische Bedeutung des 

 Sehpurpurs. Medizintsche Klinik, Nos. 25 and 26, pp. 1-19. 1905. 

 The author here gives an excellent review of the facts that support what v. 

 Kries has called the " Duplizitatstheorie," according to which the cones of the 

 retina mediate color sensation and when the light intensities are relatively high, 

 colorless sensation, the so-called "day vision," whereas the rods give us merely 

 colorless sensation, and that, moreover, only when adapted to the dark and stimu- 

 lated by light of low intensity, "twilight vision." Particularly interesting are cer- 

 tain parallels drawn from physics and a summary of the facts which show that the 

 curve for the absorption power of visual purple for the various monochromatic 

 lights corresponds closely to that for the distribution of brightness-values in the 

 spectrum (highest point in green) for the dark-adapted human eye — under exclu- 

 sive functioning of the rods. Similar curves are also obtained for the relative 

 bleaching effects of monochromatic lights on visual purple and for the action- 

 currents which they produce in the retinas of night-seeing birds. 



R. p. ANGIER. 



Maxwell, S. S. The Efltect of Salt-solutions on Ciliary Activity. Amer. Jour. Physiol., Vol. 13, 

 pp. 154-170. 1905. 

 An investigation of the relations of salt solutions to prolongation of life and 

 preservation of power to do mechanical work in the ciliated epithelium of the 

 esophagus of the frog. 



R. M. y. 



Smith, Grant. The Effect of Pigment-migration on the Phototropism of Gammarus annulatus 

 S. I. Smith. Amer. Jour. Physiol., Vol. 13, pp. 205-216. 1905. 



The author has shown that retinal pigment-migration in part determines the 

 phototropism of Gammarus. When the eyes are dark-adapted the phototropism 

 is indifferent, slightly negative or slightly positive; when they are light-adapted, 

 it is strongly positive. 



R. M. Y. 



Carlson, A. J. The Nature of Cardiac Inhibition with Special Reference to the Heart of Limulus. 

 Amer. Jour. Physiol., Vol. 13, pp. 217-240. 1905. 

 The most important conclusion adduced by Dr. Carlson from his study of 

 the nature of cardiac inhibition in Limulus is that there can be no doubt that it 

 "falls within the category of inhibition of automatic or reflex neural processes in 

 the central nervous system." In Limulus, as in the vertebrates, inhibition of the 

 heart results from the action of inhibitory nerves on the ganglia of the heart instead 

 of on the heart muscle. 



