The Sterilization of American Foulbrood Combs 25 



CONCLUSIONS 



A number of soap solutions were found unsatisfactory as carriers 

 for 20 per cent of their volume of formalin to be used as a disinfect- 

 ant for treating American foulbrood combs: (1) because of the diffi- 

 culty of controlling the reaction of the solution and of preventing the 

 precipitation of the soap and (2) because of the failure of the soap 

 solution to penetrate all cappings of sealed cells sufficiently to kill all 

 spores of Bacillus larvae contained in the diseased material therein, 

 and to do this within a period of 48 hours. 



Certain liquids of low surface tension other than ethyl alcohol, 

 such as acetone and iso-propyl alcohol, are somewhat more efficient 

 as carriers for formalin than most of the solutions tried, including 

 ethyl alcohol, as indicated by the comparatively few sealed cells 

 which failed to be completely sterilized by them within a period of 

 48 hours. On the other hand, these liquids are too expensive for 

 practical use, even if satisfactory as carriers for the formalin. Less 

 expensive liquids tried, such as a commercial methyl-ethyl ketone, 

 are unsatisfactory because of failure to sterilize scales in sealed cells 

 in 48 hours. 



Miscellaneous disinfectants such as dilute hydrochloric acid, var- 

 ious dilutions of iodine, acetic acid added to water-formalin solu- 

 tion to increase its penetrating power, and such substances as gela- 

 tine, added to water-formalin solution to increase the wetting and 

 spreading powers, are all unsatisfactory as disinfectants for steriliz- 

 ing American foulbrood combs, since none of them completely steri- 

 lizes all sealed cells in 48 hours. The hydrochloric acid solutions and 

 all but quite concentrated iodine solutions even fail to sterilize all 

 the open cells. Formaldehyde, used as formalin solution, when em- 

 ployed in sufficient proportions is the most efficient and practical 

 germicidal agent thus far used for the purpose of disinfecting 

 American foulbrood combs. A solution containing less than 20 per 

 cent of formalin is found to be unreliable. 



The results obtained with various dilutions of alcohol and of 

 alcohol-formalin solution as the carrier for 20 per cent of their vol- 

 ume of formalin are not sufficiently complete to warrant conclusions 

 as to their relative efficiency. All of these solutions are unsatis- 

 factory, since they do not completely sterilize all sealed cells in 48 

 hours. A 20 per cent solution of formalin in water, without al- 

 cohol, is ,slightly less efficient than the alcoholic solutions in steriliz- 

 ing in 48 hours the contents of sealed cells, because of its failure to 

 penetrate many of the cappings ; but it sterilizes all open cells in that 

 period. 



The commercial alcohol-formalin solution, like all the other so- 

 lutions tested, fails to sterilize completely the scales from all sealed 

 cells with a treatment of 48 hours. 



The variation in the permeability of many of the brood-cell cap- 

 pings accounts for the failure to sterilize many of the sealed cells 

 within a period of 48 hours. In some cases cappings completely 

 resist the passage of liquid or vapors into the cells, thereby making 

 low surface tension and solvent action unavailing within the period 

 of time practicable for the satisfactory treatment of combs. 



The results of experiments with glass observation cells, as well as 

 of the application of a vacuum to the solutions containing combs 



