LAURENS: MONOCHROMATIC LIGHTS. 275 
normal toads. When, after excision of the eye, the region of the eye 
was illuminated, 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 follows: 
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). 
———____—_—_—_— 
Monochromatic Blue Green Yellow Red 
lights of equal 
intensity 420-480 uu | 490-550 uy 570-620 wy 630-655 py 
Directions of | + |—j)+/0/} + |—|#/0/} + |—/+/ O/] + | — [+/0 
‘6 & ( Eye and 
© BY sain | 251°) 3% 230 | 58 194 | 94 167/121 
alg > Kye only | 246 | 42 214 | 74 187 101 160 | 126 2 
a = 2 L Skin only 296 | 88 271 |113 248 |136 217 | 166) 1 
3 3 3 ( Eyeand 
aw 2 B skin 87 | 13 80 | 20 67 | 33 58 | 42 
(3 8.| Eyeonly|) 85/15 74 | 26 Gai'35 55| 44 1 
= © (Skin only) 77 | 23 71 29 65 | 35 57 | 43 
The numbers under + indicate total numbers of reactions toward the light; 
under —, away from the light; under +, without reference to the light (indifferent) ; 
under O, no reaction within five minutes. 
