1904-5.] Niets R. FinseEN—His Lir—E AND WORK. III 
These animals are among those which dislike light, because of the ex- 
citation of the chemical rays; but how about those which like it? 
To elucidate this point eleven butterflies (pieris) were placed ‘n a large 
oblong box, half covered with red glass, and half with blue, and exposed 
to direct sunshine. At first, all beat their wings violently, but soon those 
under the red glass were mostly quiet, but those under the blue moved 
incessantly. ‘‘Later, when the sun ceased, the butterflies influenced by 
the blue light became quiet, and an hour afterwards they were disposed 
in such a manner that ten butterflies were in the blue zone and only one 
in the red.”’ Inverting the cover, ‘‘at the end of an hour eight butterflies 
were found bathed in the blue light and three remained in the red.’’ The 
experiments seemed to indicate the preference of these insects for the 
chemical rays, and the influence of these radiations upon their movements. 
Experiments with twenty or thirty meat flies (Musca vomitoria) did not 
give such positive results, ascribed to the great number and the var ety 
of their motives of movement. But towards evening they collected 
behind the red glass and slept behind it, very rarely one remained under 
the blue glass and some under the orange. Placing sugar behind the 
blue glass did not attract them to sleep there. On placing opaque plates 
before the blue glass, rendering that end of the box the darkest, and il- 
lumining the red end, all the flies but one were found in the dark part, 
showing that flies like to sleep in places where the excitation of light is 
most feeble. 
The conclusion drawn from these researches is that the action of the 
chemical rays (blue-violet) on these animals, compared with that of the 
heat rays (red), and light rays (yellow) is very considerable. It likewise 
demonstrates the extreme influence of the chemical rays upon the organism, 
which may broadly be defined as an excitation of the nervous system, 
which is so pronounced that it may provoke well-marked reflex actions 
(in the embryo), and in other instances produce very powerful and special 
reactions (in light-shunning and blanched animals) and it can truly be 
said that these chemical rays are promoters of life and energy. This action 
is constant and of daily occurrence and must be of great importance in 
the carrying on of the vital functions. Rays charged with such energy 
when absorbed by the body must have this energy transformed in many 
ways, the most marked transformation seeming to be this excitation of 
the nervous sytem, which, no doubt, influences in a secondary manner all 
the vital functions. 
If the chemical rays possess such an influence over inferior animals, 
why not over man? And so unhesitatingly Finsen says: “‘I believe im- 
plic'tly that in the future use will be made of this new therapeutic agent, 
