LAURENS: MONOCHROMATIC LIGHTS. 



275 



normal toads. When, after excision of the eye, the region of the eye 

 was iHuminated, the toads showed a large and very nearly equal per- 

 centage of indifferent reactions and failure to react. The illumination 

 of the small area of skin around the eye had, therefore, no significant in- 

 fluence upon the reactions when in normal animals the eye alone was 

 exposed to the light. The illumination of small areas of skin showed, 

 however, that the skin could be stimulated by a narrow beam of light, 

 similar to that used for stimulating only the eye, and that this sensi- 

 tiveness was approximately the same on each of the three regions of 

 the skin tested. 



E. Summary. 



The results obtained when in normal toads both the eye and the 

 skin, the eye only, and the skin only, were exposed to the lights, as 

 given in Tables 1-3 are repeated in Table 6. In Figure 2, are plotted 

 the positive responses to the different lights. These results may be 

 briefly stated as follow^s: 



TABLE 6. 



Comparison of the reactions of toads to monochromatic light received through 

 both eye and skin, through the eye only, and through the skin only (Tables 1-3). 



The numbers under + indicate total numbers of reactions toward the light; 

 under — , away from the light; under ±, without reference to the light (indifferent); 

 under 0, no reaction within five minutes. 



