THE IXFLUEXCE OF CF.RTAIX AGENTS IX DESTROYING 

 THE VITALITY OF THE TYPHOID AND OF THE COLON 

 BACILLUS. 1 



By John S. Billings and Adelaide "Ward Peckham. 



During' tlie last year a series of researches upon the influence of light, 

 of desiccation, and of the i^roducts of certain micro-organisms upon the 

 vitality of some cf the pathogenic bacteria has been carried on in the 

 laboratory of hygiene of the University of Pennsylvania by Dr. Adelaide 

 AV. Peekhani, in accordance with a general scheme for such investiga- 

 tion prepared by Dr. S. Weir Mitchell and Dr. Billings, the director of 

 the laboratory, and with the aid of a grant from the Bache fund. 



That direct sunlight kills or stops the growth of certain bacteria has 

 been known since 1877, when Dowiies and Blunt presented to the 

 Boyal Society a report on "Researches on the effect of light upon bac- 

 teria and other organisms."^ Since that date a number of papers on 

 this subject have been published, the most important one in relation to 

 the typhoid bacillus being that of Janowski in 1890.^ The first series of 

 exi)eriments by Dr. Peckham was made with the staphylococcus pyo- 

 genes aureus, the object being mainly to determine the best methods of 

 investigation. 



Photobacteriographs were made by Buchner's method, namely, by 

 placing a square of black paper, or of glass of different colors, upon 

 the bottom of a plate containing inoculated agar-agar during insola- 

 tion ; but although the protected portion was visible after fifteen min- 

 utes' insolation and incubation for twenty-four hours, and sharply 

 defined after two hours' insolation and incubation as before, no accu- 

 rate estimate could be made of the difference in the destructive power 

 of difterent periods of insolation. Successful photobacteriography 

 re(iuires inoculation of large quantities of bacteria, in order that the 

 colonies may be set so closely together that a ground-glass appearance 



'[Au article under this title by the same authors was iirinted in Science, Feb- 

 ruary 15, 1895.] 



-rroc. Roy. Soc. 1877, Vol. XXVI, page 488. 



■''Zur Biologic der Typhus Bacillen, Centralbl. f Bakteriol, etc., VIII, 1890. pages 

 167,193,230,262. 



451 



