Finsen, Niels R.
Aiton's Encyclopedia (1910)
Niels R. (1861-1904), a distinguished Danish scientist. He was born on one of the Faroe Islands and died at Copenhagen. While a student in the University of Copenhagen Finsen began experiments on the influence of sunlight and electric light upon the diseases and blemishes of the skin. In 1890 he asserted that smallpox could be cured by admitting light to the sick room through red curtains. In 1894 an epidemic of smallpox prevailed in the city. This disease is due, it is believed, to the presence of hordes of inconceivably small animals in the body of the sick. The pock marks in the faces of victims are made by colonies of these protozoans, as they are called. Finsen demonstrated that red light not only killed out the germs in these spots and prevented patients from being marked, but also exterminated them from the system. Two years later, 1896, the authorities of the city hospital of Copenhagen were so far convinced that red light was a cure for small pox that rooms were fitted up for this method of treatment and the Danish government took up the matter, endowed an institution, and placed it at the disposal of Professor Finsen. This distinguished student made still another discovery,--that certain chemical rays, not Roentgen or X-rays, are a cure for the less virulent or surface forms of cancer. It would require pages to describe the experiments and the ray-producing devices of Professor Finsen. It is sufficient to know that patients pass day after day in easy invalid chairs, in large airy rooms, while attendant nurses manage lenses and focus rays from Finsen instruments on the cancerous spots hours at a time until the cancers are killed and the lives of the patients saved. Queen Alexandra of England, who, it will be remembered, is Danish by birth, paid the expense of installing the Finsen cure in a London hospital. Finsen treatments for smallpox and surface cancer are almost as well known as that of Pasteur for rabies or hydrophobia. It is too soon to say that these diseases have been mastered; but many famous cures have been effected and life has been saved. Reports from Finsen Institutes in London, Paris, Berlin, and Copenhagen claim that fiftyone per cent, or a little over one-half, of the patients who have attended these hospitals have been cured. See Smallpox
What Has Changed in the Last Century
Aiton's, writing in 1910, explained smallpox as "hordes of inconceivably small animals" — protozoa — that Finsen's red light killed off; smallpox is in fact caused by a virus, and controlled trials in the 1970s found red-light treatment gave no benefit at all. The disease Finsen genuinely did treat was lupus vulgaris, tuberculosis of the skin (the article's "less virulent or surface forms of cancer" is a misdescription), and for that concentrated ultraviolet work he won the 1903 Nobel Prize in Physiology or Medicine, the year before his death. Both conditions have since been overtaken: antibiotics such as streptomycin and isoniazid made lamp therapy for skin tuberculosis obsolete from the late 1940s, and smallpox itself was declared eradicated by the World Health Organization in 1980. Finsen's core idea survives, though — light as medicine is now routine, in UVB therapy for psoriasis and blue-light treatment of newborn jaundice.
Written for this edition, 2026.