SACBROOD. 



35 



In performing these experiments a crushed mass, 

 representing from 10 to 20 larvae recently dead of the 

 disease, is diluted to about 10 times its volume with 

 tap water. About one-half ounce of this suspension is 

 placed in a test tube (fig. 31), almost filling it. The 

 tube is stoppered with a perforated cork, bearing a 

 short glass tube of small caliber and drawn at one end 

 to capillary size. This is all immersed in water at a 

 temperature to which it is desired that the virus shall 

 be heated. It requires nearly five minutes for the tem- 

 perature of the suspension in the tube to reach that of 

 the water outside. After reaching the degree desired 

 the temperature is maintained for 10 minutes, after 

 which the tube is removed and the contents added to 

 about one-half pint of sirup. The suspension is then 

 fed to a healthy colony. If by such a feeding no sac- 

 brood is produced, the virus is considered as having 

 been destroyed by the heating. On the other hand, 

 if the disease is produced it follows naturally that the 

 virus had not been destroyed. 



HEATING REQUIRED TO DESTROY SACBROOD VIRUS 

 WHEN SUSPENDED IN GLYCERINE. 



In determining the amount of heating that is necessary 

 to destroy the virus of a disease when it is suspended 

 in a liquid, the results should always be given in terms 

 of at least the three factors, (1) degree of temperature, 

 (2) time of heating, and (3) the medium in which the 

 virus is suspended. 



With the virus of sacbrood the results vary markedly, 

 depending upon the nature of the liquid in which the 

 suspension is made. To illustrate this point the re- 

 sults of a few inoculation experiments are given here 

 in which the virus was heated while suspended in 

 glycerine. 



Table II. — Effect produced by heating the virus of sacbrood suspended 

 in glycerine. 



Date of inoculation. 



Temperature. 



Time of 

 heating. 



Results of inoculation. 



June 25, 1915 



°F. 

 140 

 149 

 158 

 160 

 163 

 167 



°C. 



60 

 65 

 70 

 71 

 73 

 75 



Minutes. 

 10 

 10 

 10 

 10 

 10 

 10 



Sacbrood produced. 

 Do. 

 Do 



June 24, 1915 



June 25, 1915 



Aug. 28, 1915 



Do 



Do 



No disease produced. 

 Do 



Aug. 7, 1915 







s o 



o .s 

 PS 



% P. 



~ si 



O *2 



1* 



If 



II 



