192 



Millard summarized his result by stating that they can not be con- 

 sidered a satisfactory demonstration of the efficacy claimed for the 

 Danysz virus. The results indicate a rapid loss of virulence, which 

 must be obviated if this virus is to be of utility for rat destruction. 



Again, in 1907, during the seventh outbreak of plague in Sydney, 

 Thompson" had Millard test the preparations known as azoa and ratin. 

 The laboratory results with these preparations were similar to those 

 made by other investigators. Experiments made upon the ship 

 Hartfield with azoa produced no considerable epizootic. The fatality 

 among such rats as were infected was small. The practical tests with 

 azoa upon several areas along the harbor front also resulted in disap- 

 pointment. 



The tests made with ratin upon the bark Quilpe produced no 

 epizootic among the rats, and of the rats caught none of them showed 

 infection; and the field experiment at Gladesville also resulted nega- 

 tively so far as dead or sick rats were concerned. Nevertheless, there 

 was apparently considerable diminution in the rat population of this 

 area. 



Foster, 6 1908, reports unfavorably upon the results of tests made 

 of some of these rat viruses. Laboratories were opened for the use of 

 different parties who wished to make tests. The tests were conducted 

 under their own supervision. The rats which were not fed on any- 

 thing but grain died as freely as those that had been fed on azoa. 

 So far as this preparation is concerned Foster states that it is abso- 

 lutely useless to depend upon it. 



Several reports are found in print in which the rat virus was laid 

 out in certain localities and shortly afterwards the rats disappeared 

 at least no more were noticed. Such observations are apt to be mis- 

 leading, for rats are migratory. They come and go, especially when 

 disturbed. Further, it is doubtful, as far as plague is concerned, 

 whether it is desirable to drive the rats away, for they may thus scatter 

 the infection. 



S. S. Mereshkowsky and E. Sarin c have recently studied ratin II, 

 put out by a Copenhagen firm " Bakteriologisches Laboratorium 

 Ratin." The label upon the can of ratin II states that it is a bac- 

 terial culture, which produces in rats an infectious and fatal disease, 

 killing them in two to eight days. The samples used by the authors 

 were obtained as needed from the St. Petersburg representative of 

 the firm. Feeding experiments carried out with gray rats (Mus de- 



a Thompson, J. Ashburton: Report of the board of health on plague in New South 

 Wales, 1907. On a seventh outbreak of plague at Sydney, 1907. Legislative Assem- 

 bly, N. S. W., 1908. 



b Foster, N. K.: The danger of a general plague infection in the United States. 

 Proc. Confer. State and Prov. Boards of Health of N. America, 1908, p. 15. 



c Ueber das Ratin II. Centralb. fur' Bakt. Parstk. u. Infectsk. Originale. Bd. 

 51. Heft 1. July 17, 1909, p. 6. 



