February 15, 1695.] 



SCIENCE. 



173 



micro-organisms, were not only killed, but 

 the material was completely harmless when 

 inoculated into white mice. It was, how- 

 ever, possible to obtain vigorous and viru- 

 lent growths from cultures which had been 

 made quite innocuous by the action of the 

 Bun. Oxygen was used up in the process. 

 Under ordinary circumstances one might 

 be tempted to explain the effect of sunlight 

 in destroying bacteria by the drying of the 

 organisms exposed to it, especially in the 

 case of those bacteria which do not form 

 spores, but our experiments show that 

 desiccation for months has little effect on 

 the vitality of the typhoid or of the colon 

 bacillus. To detei-mine the influence of 

 desiccation upon these organisms, and also 

 upon the ataphylococcKs aureus, the following 

 experiments were made : 



Bouillon cultures of the baciUiia typhi ah- 

 dominalis, the hacillus coli communis and the 

 staphylococcus anreus were roughly dried on 

 threads one centimetre long and then desic- 

 cated, a portion lieing placed in a vacuum, 

 another portion in a desiccator over sul- 

 phuric acid, and a third in a closet ; all 

 were kept in the dark. The result of the 

 desiccation under the tliree different condi- 

 tions is as follows : 

 Bacillus typhi abdoiniiialin : 



Lived in a vacuum from December .30 

 until July 24, or 207 days. In a desic- 

 cator over sulphuric acid from January 

 3 until July 24, or 213 days. 



In a closet from December 18 until July 

 24, or 229 days. 

 Bacillus coli communis: 



Lived in vacuum from November 29 to 

 May 30, or 183 days. 



In a desiccator over sulphuric acid from 

 January 3 until Julj- 24, or 213 days. 



In a closet from December 30 until May 

 30, or 152 days. 

 Staphylococcus aureus : 



Lived in vacuum from November 29 until 

 July 24, or 207 days. 



In a desiccator over sulphuric acid fi-om 

 October 2.5 until April 19. or 178 days. 



In a closet from February 13 until July 

 24, or 162 days. 



It will be seen from these experiments 

 that the organisms experimented on endure 

 desiccation for five mouths, or more, with- 

 out losing their ^^tality. and hence the slight 

 evaporation which may have occurred in 

 the insolation experiments, had probably no 

 influence on the results. 



It is evident that sunshine must exercise 

 considerable influence in destroying bacteria 

 on the surface of soU, streets, etc., exposed 

 to its influence, but its action is almost con- 

 fined to the surface, as appears from the re- 

 sults obtained by Esmarch in attempts to dis- 

 infect bedding and clothing by this agency. 

 While the light from an incandescent elec- 

 tric lamp has little germicidal effect, tliat 

 from a powerful arc lamp produces eft'ccts 

 similar to those of sunlight, and it has been 

 proposed to use this means to disinfect the 

 walls of infected rooms. The bacillus of 

 tuljerculosis appears to be more quickly de- 

 stroyed by light than the typhoid or the 

 colon bacillus, being killed by exposure to 

 simple diffused daylight in about a week,* 

 and this fact should be borne in mind in ad- 

 vising measures to prevent the diffusion of 

 this organism. 



The investigations ujion the typhoid and 

 the colon bacillus referred to in this paper, 

 were undertaken as part of a general scheme 

 of inquiry to ascertain the agencies which 

 tend to detroy the tjiihoid bacillus when it 

 is introduced into a source of water supply, 

 as, for example, into a running stivam. 

 An important part of this investigation 

 relates to the influence of the common 

 water bacteria, or of their products, upon 

 the vitality of the typhoid bacillus. 



This research was conducted as follows : 



* Uebor Ixactcriologisclic Forachung : Vortra); in der 

 ersten allgem. Sitznng des X intemationalen Con- 

 gress, 1890. 



