88 SUMMARY OF CURRENT RESEARCHES RELATING TO 



pellicle on broth ; on pepton agar it develops a strong odour of 

 trimethylamine ; it is aerobic. 



Bacterial Rot of Potato.* — F. C. Harrison has isolated a bacillus 

 from potato rot. The organism was cultivated upon a large number 

 of media, and many varieties of vegetables became affected after 

 inoculation. Only slight growth occurred under anaei'obic conditions ; 

 fifty minutes' exposure of agar plates to sunlight served to inhibit the 

 production of colonies ; optimum temperature 2.3°-28° C. ; good 

 growth was obtained at 40^ F. (4 -44° C.) and slight growth in cold 

 storage room at 35° F. (0" 56° C). The thermal death point was 54° C. 

 for 10 minutes. 



There was slight production of indol in Dunham's solution on 

 warming, after 7 days' growth at 25" C. After a days at 25° C. in 

 nitrate broth, abundant nitrite had been produced. It was nonpatho- 

 genic for laboratory animals. 



The author suggests the following precautions against the disease : 

 plant rot resisting varieties and seed free from all rot, in well drained 

 land ; reduce number of insects by Paris green, and growth of fungi by 

 Bordeaux mixture ; rotation of crops. 



Bacterioscopic Analysis of Excremental Pollution.t — A.MacConkey, 

 referring to E. Klein's note, J points out that the first kind of bile salt 

 broth was one containing not glucose, but lactose, which was to be 

 preferred if search is being made for typical B. coli only. The change 

 to glucose was made so as to include other organisms such as 



B. enteritia 



The addition of " Fleischwasser " or of " beef extract," decreases the 

 selective action of bile salt media, and it is upon this selective action 

 that the value chiefly depends. B. ppstis and B. ps(>ii4o-tuberctdosis 

 rodentium grow well, but the bacilli of fowl cholera show very little, if 

 any, multiplication on bile salt media. The author finds that the 

 selective action extends to different strains of the same bacillus, a 

 virulent B. typhosus growing better than a nonvirulent one. 



The Occurrence and Distribution of Azotobacter chroococcum in 

 different soils. § — H. R. Christenseu finds that the occurrence and 

 distribution of this organism is connected with the amount of calcium 

 carbonate in the soil. From the amount of growth of Azotobacter 

 from a definite amount of soil in a nutrient fluid medium containing 

 mannite and phosphate of Ciilcium it is possible to obtain a biological 

 expression of the calcium carbonate content of the soil ; but this can be 

 more accurately obtained by using pure culture of Azotobacter. Certain 

 phosphates of calcium and sodium are favourable to the growth of 

 Azotobacter ; the relations of its growth to phosphates and different 

 salts of calcium seem to justify the expectation that it may be possible 



* Centralbl. Bakt., 2te Abt. xvii. (1906) p. 384. 



t Brit. Med. Journ. 1906, ii. p. 1521. 



X See this Journal, 1906, p. 72S. 



§ Centralbl. Bakt., 2te Abt. xvii. (1906) p. 378. 



