240 BOARD OF AGRICULTURE. [Pub. Doc. 



other because it has a strong bleaching action on textile fabrics. 

 Sulphur dioxide has a less marked bleaching action, and is 

 recommended by the public health authorities for fumigating 

 ships for the purpose of destroying rats to prevent the intro- 

 duction of bubonic plague. Port regulations prescribe its use, 

 and steamship companies provide vessels with special apparatus 

 for generating the gas. For directions for fumigating vessels 

 with sulphur see Public Health Reports, June 20, 1913, "The 

 Fumigation of Vessels for the Destruction of Rats," by S. B. 

 Grubbs and B. E. Holsendorf, and "The Rat in Relation to 

 Shipping," by Wm. C. Hobdy, published in "The Rat and its 

 Relation to the Public Health," by various authors. Public 

 Health and Marine Hospital Service, Treasury Department of 

 the United States, 1910, page 211. 



Rat Viruses. 



The Massachusetts State Board of Agriculture has not ex- 

 perimented with any bacterial infection, but has interviewed 

 many people who have done so, and only three have reported 

 satisfactory results. Careful experiments have been made with 

 viruses by scientific investigators in this country, and the 

 general verdict seems to be against their effectiveness. 



Dr. M. J. Rosenau, Professor of Preventive Medicine, 

 Harvard University Medical School, has made many experi- 

 ments with various viruses advertised commercially. He has 

 experimented with the bacillus obtained by Danj'sz and the 

 commercial cultures known as ratite, azoa and ratin. 



In the laboratory some of these viruses have been effective 

 to a considerable degree under favorable conditions, but Dr. 

 Rosenau does not recommend them for general use for the 

 following reasons: (1) "Rats are notoriously resistant to bac- 

 terial infection." (2) The Danysz virus, which is pathogenic 

 for rats under laboratory conditions, has feeble power of 

 propagating itself from one rat to another; it quickly loses its 

 virulence, especially when exposed to outdoor conditions; the 

 other viruses have proven even less satisfactory in this respect. 

 (3) The claim that these rat viruses are harmless to man needs 

 revision, in view of cases of sickness and death resulting from 

 their use reported by various observers. 



