77 



Under natural conditions these rat \iruses appear to act 

 somewhat like a chemical poison. They have, however, these 

 great disadvantages: they are comparatively expensive, and 

 when taken in small amounts or after they have lost virulence 

 they render rats immune. 



The Biological Survey of the T'nited States Department of 

 Agriculture in co-operation with the Bureau of Animal In- 

 dustry has experimented with ratin in both laboratory and field. 

 The material (ratin Xo. 2, labeled "Trans- Atlantic Ratin") 

 was furnished by the American agents in New York. This was 

 claimed to be a bacterial preparation which would kill for six 

 generations, but according to Dr. Rosenau, Professor Lantz 

 says that it proved to be a glucoside poison (probably squill), 

 and that it contained no bacteria. 



Squill is an effective rat poison, and this proved to be such, 

 although in some of the experiments a considerable percentage 

 of the affected rats recovered, and subsequent attempts to 

 kill them with this material failed. More than lOO rats were 

 used in the experiment. 



Dr. Rosenau says that the effect of this ratin is not com- 

 municable, as it is a poison and not a virus. 



Ratin Xo. 1 (a real bacterial culture) was fed to rats and 

 produced no apparent result. Several trials of azoa for the 

 destruction of rats have been observed by the members of the 

 Biological Survey. In some of these cases no results were 

 noted. In one there was some measure of success. Experi- 

 ments with the various rat viruses during the outbreak of the 

 plague in San Francisco gave unsatisfactory results.^ 



Dr. C II. Townsend recently has published in "Bird-Lore" 

 a report of success with the so-called Pasteur virus, but in reply 

 to an inquiry he writes now that the second trial was dis- 

 appointing. Dr. Rosenau writes that he now sees no reason 

 to modify his conclusions as given above. Scientists may yet 

 find a virus that will be effective under ordinary conditions, 

 but thus far the efforts in this direction seem to have met with 

 disappointment. 



1 The Rat and its Relation to the Public Health, by various authors, Treas. Dept., Public 

 Health and Marine Hospital Serv. of U. S., 1910, pp. 186-188. .See also Lantz, David E., U. S 

 Dept. Agr., Biol. Surv. Bull. .33, 1909, pp. 50, 51. 



