28 



Formic acid agar was then made containing the same proportion of 

 formic acid as was found in the first sample of buckwheat honey, and weaker 

 formic acid agar containing the same percentage of formio acid as was present 

 in the first eample of clover honey; and tpires placed upon the stronger 

 formic agar did not germinate, while on the weaker formic agar the germina- 

 tion was only slightly retarded ; and after the weaker agar was two days in 

 the incubator, there was a large growth. Spores transferred from the strong 

 formic agar (after being in contact with it for six days in the incubator) failed 

 to grow on the weaker formic agar within two days ; but after four days in 

 the incubator they grew abundantly. The culture growing on the weaker 

 formic agar was then transferred to the strong formic agar, to ascertain 

 whether the germ could be accustooied to more unnatural food by previous 

 cultivation on the weak formic agar. This transfer was, however, un- 

 successful. 



The germs used in these tests were isolated from samples of diseased 

 comb from Ontario, Austria and Florida, U.S.A. 



Formic acid bouillon was also made containing .15% of formic acid ; and 

 spores kept in this brolh for eight months continued to germinate when 

 transplanted to suitable matprial. 



Formic acid agar was likewise made in the same proportion as snggestt d 

 by Bertrand (69); that is, formic acid 10, water 90; and a tablespoonful of 

 this mixture to a litre of syrup ; but instead of syrup, agar was used. Fifteen 

 c.c. of this acid agar was poured into each Petri plate, and the surface inocu- 

 lated with spores. 



E( suits : On 14 plates, no growth. 



On 2 plates, very restricted growth, limited toons-eighth of an 



inch of the needle track (60 houre). 

 On control plates, abundant growth. 



From these investigations, viz., the analysis of the honey, the experi- 

 ments based thereon, and the tests with agar made in the proportion sug- 

 gested by Bertrand, we would note three things : (1) That the amount of 

 formic acid recommended by Bertrand for the cure of foul brood is almost 

 identical with the amount found in buckwheat honey ; (2) that formic acid is 

 a good antiseptic ; (3) that the formic acid in buckwheat honey may possibly 

 tend more or less to ward oflf foul brood. 



We may add that our analysis, showing a larger proportion of formic acid 

 in buckwheat honey than in clover honey, is an interesting explanation of a 

 fact well known among practical bee-keepers, viz., that the sting of bees when 

 working on buckwheat is much more irritant than when working on clover. 



In conclusion under this head, we may say that formic acid has given 

 good results when used in the treatment of foul brood ; and it is in a S'inse a 

 natural remedy, being manufactured to some extent by the bees themselves. 



(12) Other substances used for trealing this disease. Among other sub- 

 stances that have been used for treating this disease are sulphuric acid, sul- 

 faminol, various modifications of substances already mentioned, and some rec- 

 ommended in the McLean method (80), the Muth method, and others ; but 

 these have not had so wide application as those referred to in the preceding 

 paragraphs. 



Experiments on the Use of Drugs for Combatting the Disease. 

 I have already mentioned that, in one of my experiments, I endeavoured 

 to find out if the viruleace of the germ was attenuated by prolonged culture 

 in artificial media, with the result that considerable attenuation occurred 



