ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 657 



and practically re-written. The work deals with the simple and 

 compound Microscope, the choice of a Microscope, objectives and 

 eye-pieces, accessory apparatus, the practical optics of the Microscope, 

 the manipulation of the Microscope and its accessories. The volume 

 may be heartily recommended as a useful guide to beginners. 



B. Technique.* 

 (1) Collecting: Objects, including- Culture Processes. 



Formate Broth in the Differential Diagnosis of Micro-organisms.| 

 W. Omelianski refers to the differentiating properties of media contain- 

 ing alkaline salts of formic acid in the diagnosis of micro-organisms. 

 Whereas most pathogenic forms behave negatively or passively, the 

 nearly allied non-pathogenic bacilli split up the formate, with the de- 

 velopment of gas, C0 2 and H, and the formation of carbonates. If 

 phenolphthalein has been added to the medium, the increased alkinity 

 will be shown by the appearance of a red coloration ; but this redden- 

 ing of the medium occurs not only from the splitting up of formates, 

 but also by the decomposition of albuminous substances in the medium. 

 Cultures of B. coli and B. typhi grown on this medium (formate agar 

 bouillon) both produce a red coloration, which in the case of B. coli 

 is more intense and appears earlier. The weaker and later appearing 

 redness of the culture of B. typhi is not because this organism de- 

 composes the formate more slowly, since it has no action on these salts, 

 but is due entirely to the formation of alkaline decomposition products of 

 albuminous substances ; in the same manner is explained the reddening 

 of the medium with cultures of B. facalis alcigenes and B. dysenteries 

 Flexner. The author has contrived to set aside this objection by 

 estimating the amount of gas produced by the cultures, using for this 

 purpose an arrangement of Einhorm's saccharometer. The medium he 

 uses is ordinary pepton broth, with the addition of • 5 p.c. of sodium 

 formate. 



With six different strains of B. typhi abdominalis, and by making all 

 possible variations — both as to the strength of the formate present and 

 the age of the culture used — -he was in no instance able to show the 

 slightest evidence of any decomposition of the formate. All cultures 

 of B. coli communis showed energetic destruction of the formate with an 

 abundant production of gas ; with cultures of paratyphoid A and B the 

 decomposition of the salt and production of gas were equally energetic ; 

 five different strains of B. dysenteric^ behaved like those of B. typhi, 

 producing not the slightest decomposition of the formic salt. 



Identification of Colonies of Pneumococcus.l — L. Buerger prepares 

 the following media : neutral agar made from meat juice, and contain- 

 ing 1 * 5-2 p.c. of pepton, and 2 ' 5 p.c. of agar, is melted down, and, 



* This subdivision contains (1) Collecting Objects, including Culture Pro- 

 cesses; (2) Preparing Objects; (3) Cutting, including Imbedding and Microtomes ; 

 (4) Staining and Injecting; (5) Mounting, including slides, preservative fluids, Ac; 

 (6) Miscellaneous. t Centralbl. Bakt., 2 W Abt., xiv. (1905) p. 673. 



% Centralbl. Bakt., 1" Abt., xxxix. (1905) p. 20. 



