iu TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vou. VIII. 
and the proof experiment once made, it will be easy to carry it out practi- 
cally under the form of light baths; and lastly to determine whether they 
are to be blue or violet, the variations in their strength and duration, 
and whether natural or artificial.’’ In this connection Finsen noted that 
‘light baths had been used in antiquity, and that General Pleasonton had 
used blue light to cultivate v nes and other plants, for rearing animals, 
and as baths for the sick; not however pure blue, for every blue square 
there were three clear ones. His book was published in Philadelphia in 
1877, under the title of ‘‘The Influence of the Blue Ray of the Sunlight 
and of the Blue Color of the Sky in Developing Animal and Vegetable 
Life, in Arresting Disease, and in Restoring Health in Acute and Chronic 
Disorders to Human and Domestic Animals.’’ He had concluded that 
since the sky was blue this colour must be of great importance to animals 
and plants, and he also discussed the remarkable chemical qualities of the 
blue rays. Finsen remarks of him: ‘‘He thus approached the truth; 
but his faulty experiments, and, above all, his tendency to look upon 
blue light as a universal panacea—the very title of his book indicates this 
—have not contributed to show the value of a biological agent whose 
importance is beyond discussion. ‘The General’s book, printed on blue 
paper and bound in blue, makes one think, however favorably disposed 
one might be, that its contents could hardly fail to be ‘coloured’ also.”’ 
As a final argument on behalf of light Finsen cites the special effects 
of direct sunlight upon all organisms. ‘‘Sudden transitions from a cloudy 
to a clear sky make us feel it much more than continuous sun. If the sky 
has been overcast for part of a day, and the sun suddenly comes out, it 
is as if nature has been brought to life. The insects fly and hum gaily; 
the reptiles bask in the bright sunlight; the birds chirp; and we ourselves 
get a feeling of well-being and of fulness of life. This somewhat indefin- 
able effect is none the less very marked. One might say that light is an 
‘exciter of life,’ in the sense that it excites living activity and promotes 
movement. I believe I am right in saying that this quality has hitherto 
been attributed to the ‘psychical’ action of light and to that of heat. It 
seems to me that both my positive and negative experiments have suffi- 
ciently shown that we ought to refer the greater part to the chemical rays, 
which possess a stimulating influence on the lower animals.”’ 
This later work which we have been considering deals with researches 
carried on in the spring and summer of 1894, and published in February, 
1895, and is only a mere fragment of a series of observations which he was 
conducting, but being interrupted, was unable to continue. In 1899 he 
published an Appendix to this paper, in which he detailed experiments 
carried out in the spring of 1895, in which he observed strong secondary 
effects of light upon the embryos of the frog which seemed to supplement 
