DEVELOPMENT IN NINETEENTH CENTURY 319 



certain malignant diseases, notably cancer of the skin and sarcoma, 

 especially when the disease cannot be treated by ordinary means. 

 It does not appear to have been of any special value in other forms 

 of cancer located in the organs of the body. The Rontgen ray has 

 also been employed as a depilatory, also to bring about atrophy of 

 the glands of the skin and to relieve pain. The Rontgen ray also is 

 used to cure pseudoleukemia and splenomedullary leukemia, rodent 

 ulcer, lupus vulgaris, and chronic eczema. 



Great credit belongs to our distinguished chairman for the mag- 

 nificent work which he has performed in the application of the 

 Rontgen ray to surgery, and his writings upon this subject are worthy 

 of close study. 



The Finsen light is a discovery which was made about 1897, by 

 means of which certain forms of cutaneous disease of an infective 

 origin, notably lupus, have been cured. This result is accomplished 

 by means of a light which can be employed without accompanying 

 heat, and which causes an inflammation of moderate intensity upon 

 the skin. Sunlight fails to destroy bacteria, owing to the presence of 

 heat, while the Finsen light, deprived of heat, effects a cure. 



In 1878, Blunt and Downes proved the efficacy of chemic rays of 

 light to kill bacteria. Finsen demonstrated that the action of light 

 was increased if it be applied through rock-crystal lenses, and the 

 heat absorbed by passing it through a violet-colored liquid and 

 water, while the part of the body to be treated is made anemic by 

 pressure. Finsen apparatus increased the efficacy of the violet or 

 chemic rays, and absorbed red or heat rays. The effect of light upon 

 bacteria is slow in its operation, but its rapidity is increased by con- 

 centration, by means of mirrors or by lenses. The heat-rays, such as 

 ultra-red, red, orange, or yellow, must be eliminated, as they burn the 

 tissues, while the blue or violet rays destroy the bacteria. The arc 

 electric light comes next, and is now often used because it can be 

 obtained at all times. The incandescent light is of no value, owing to 

 the fact that it possesses too few chemic rays. The electric light 

 requires a special apparatus for its use, since its rays are divergent 

 and not parallel, as is the case in the sun's rays. Professor Pupin 

 says that the time is not far distant when a new method of producing 

 light of short wave-length will be perfected, which will be far more 

 powerful than the Finsen light. The shortcomings of the present 

 method of producing light of great actinic power consist principally 

 in the absorption of this light by the glass of the vacuum tubes in 

 which it is produced. Within the last year a method has been dis- 

 covered of fusing quartz, and blowing it out by means of the oxy hy- 

 drogen flame into bulbs, which are used for electric vacuum tubes. 

 Quartz, as is well known, absorbs light of short wave-length to a very 

 slight extent, and it is the light of short wave-length which is em- 



