ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 695 



subject, which on gelatin exhibits raised colonies with filmy irregular 

 margins, and the bacilli of which are cylindrical in shape when taken 

 from recent cultures ; and (2) a less virulent type, bred in the rat, 

 exhibiting rounded translucent colonies on gelatin, with coccus-like 

 forms on culture. He regards the rat-bacillus of Edington as belonging 

 to the latter type. With regard to the supposed flea agency in the 

 spread of plague among rats, the author, from the results of experiment, 

 negatives it. He emphasises the prevalence of wounds, abrasions, 

 ulcers, etc., in the majority of sewer rats, making ready inoculation 

 possible. From the fact that the bloodvessels and uriniferous tubules of 

 the kidney in a plague-infected rat contain B.pestis, he considers the 

 urine as a possible source of infection. He has found the sanguineous 

 mucus of the intestine very virulent, and also, in the sxtb-acute form, the 

 oral and pharyngeal mucus. Feeding with infected material gave nega- 

 tive results. The author discusses four rat-diseases other than plague : 

 (1) that described by Danysz, caused by a microbe shown to be a variety 

 of B. coli ; (2) one caused by a microbe related partly to B. coli and 

 partly to B. lactis ccrot/enes, and named by him Bad. Bristolensp ; (3) 

 Pseudotuberculosis ; and (4) a disease caused by a micro-organism 

 apparently morphologically identical with Klebs-Loffler's B. diphtheria, 

 which is uninfluenced by diphtheria anti-toxin. 



Nitrifying Organisms in Sewage Filters.* — Schultz-Schultzenstein 

 has carried out a research with the object of isolating and studying the 

 nitrifying bacteria in sewage filters, and comparing them with the 

 nitrifying organisms present in the soil of cultivated fields. His con- 

 clusions are as follows : (1) on the coke of biological filters Winogradsky's 

 nitrifying organisms are present ; (2) for their isolation the silica jelly 

 media of Winogradsky is strongly recommended ; (3) the micro-organisms 

 isolated by Winogradsky are introduced into the filters by the sewage 

 itself ; (4) no nitrifying organisms other than those discovered by 

 Winogradsky were found upon the coke of biological filters ; (5) steri- 

 lised sewage containing ammonium salts may be kept indefinitely without 

 losing ammonia. If such sewage be inoculated with the nitrite- and the 

 nitrate-formers, the ammonia is soon oxidised ; (G) unsterilised sewage 

 kept without inoculation loses its ammonia in time. Nitrites and 

 nitrates make their appearance, and these disappear after some time 

 (denitrification) ; (7) the optimum temperature for the nitrifying 

 organism lies between 28° C. and 30°-C. ; (8) slight amounts of organic 

 acids up to • 1 p.c. interfere but little with the growth of the nitrifying 

 organisms ; they retard their nitrifying activity only. Commercial 

 chloride of lime and phenol up to O'l p.c. act similarly ; (9) 0*5 p.c. 

 solutions of organic acids, of phenol, chloride of lime and inorganic 

 acids, completely prevent growth and nitrification ; (10) free ammonia 

 entirely prevents the growth and activity of the nitrifying organisms. 



Role of Streptococci in the Course of Scarlatina.f — Besredka and 

 Dopter have endeavoured to demonstrate specificity as regards the 

 streptococci commonly found in the throat and heart's blood of cases of 



* Technology Quarterly, xvii. (1904) pp. 1SG-203. 

 t Ann. Inst. Pasteur, xviii. (1904) pp. 373-7. 



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