This is a small book of 79 pages containing Finsen's papers on, 1, the chemical rays of light and smallpox; 2, light as a stimulant; 3, the treatment of lupus vulgaris by concentrated chemical rays. An editorial abstract of the French issue appeared in The Journal, Sept. 15, 1900. The profession in general are probably well acquainted with the favorable opinion of those best qualified to judge of Finsen's light treatment of lupus. The appendix by the translator gives the results obtained up to the present time. The book is interesting reading and may be said to be the cornerstone of phototherapy.