118 TRANSACTIONS OF THE CANADIAN INSTITUTE. (Vou. VIII. 
he used an arc-light of 80 amperes, and had his lenses constructed of rock 
crystal, (quartz) which allows the ultra-violet rays, which are absorbed 
by ordinary glass, to pass; the power of these rays to destroy germs being 
much greater than that of the v:sible chemical rays. The effect of these 
improvements was to increase the curative effect, as well as the rapidity 
of treatment. With it he was able to kill the bacillus prodigiosus in one 
minute, and a lupus the size of a pea disappeared completely after a 
fifteen to twenty minute exposure. Unfortunately, rock crystal lenses are 
expensive and can only be obtained of small dimensions.* Further im- 
provements n the apparatus consisted in placing an additional cooling 
chamber surrounding the lower portion of the tube; and also the distilled 
water chamber between the lenses. By means of inlet and outlet tubes 
connected by rubber tubing to a source of water supply, the cold water 
thereby kept circulating in the chamber kept the distilled water between 
Fic. 3—Diagram showing Improved Tube, its relation to the are and cooling device of pressure lens. 
the lenses cool, otherwise it became boiling hot. But in spite of this 
extra cooling device the light was still too hot for the patient, so Finsen 
devised a hollow compressor, consisting of a plate of rock crystal (quartz), 
and a plano-convex lens of rock crystal, set in a conical ring, leaving a 
space between; an inlet and an outlet tube in the ring permitted a con- 
stant supply of cold water; by means of arms projecting from the ring, 
the compressor could be either firmly fastened on, or held by the attendant 
nurse. ‘The pressure exerted upon the part, driving the blood out of it 
and thereby permitting better penetration of the chemical rays, which 
passed more readily through the crystal and contained water than through 
the former glass. 
Finsen recognized that the method was capable of much improve- 
ment, the greatest drawbacks being the length of time occupied by each 
* ‘Quartz is very prone to break along its line of crystallization and the cutter never knows when 
this accident may befall. The author has been informed that as much as a ton of quartz was used befor 
a perfect single focal lens of quartz two inches in diameter was obtained.”’ Cleaves’ ‘‘ Light Ener gy.” 
