ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 361 



As the drop is blackish it is easily seen and focused. The solution is 

 said to be harmless to bacteria. 



Bacteriolog-ical Examination of Suspected Cholera-carriers.* — 

 A. J. Bendick advocates the use of the following procedure : — To a 

 litre of water add 10 grm. of peptone and 5 grm. sodium chloride ; boil ; 

 titrate with phenolphthalein to a neutral reaction ; add 1 grm. of 

 anhydrous sodium carbonate ; boil ; filter through double filter-paper ; 

 add 5 grm. of saccharose and 5 cc. of a 50-p.c. alcoholic-saturated 

 solution of phenolphthalein ; tube and sterilize by fractional steriliza- 

 tion in an Arnold sterilizer. The technique is as follows : (1) Inocu- 

 late f feces into Dunham's peptone and incubate at 37° for 6 hours ; 

 (2) subculture 1 loop from the surface-growth into the sugar-peptone 

 and incubate for 5 to 8 hours ; (:->) plate suspicious cultures. 



If cholera vibrios be present, they are enriched by the peptone 

 medium. In the second they rapidly ferment the saccharose, the acid 

 produced neutralizes the alkali, and the red colour of the phenolphthalein 

 disappears. As soon as a tube decolorizes — which in the case of cholera 

 comes to pass within from 5 to 8 hours — a smear is made from the 

 surface, and if vibrios be present plates are made. It is stated that two 

 to three thousand specimens can be examined in one day by this 

 procedure. 



Selective Action of Media on Organisms of the " Coli " Group.! 

 C. Revis draws the following conclusions from numerous observations 

 on the "Coli" group : — 1. The types of "coliform " organisms which 

 appear on inoculation of dilutions of milk, etc., into bile salt-glucose 

 tubes are the result of a combination of mutual toxic action, acid 

 development, and the nature of the medium. 2. There is undoubted 

 suppression of feeble organisms, particularly of those which can only 

 produce acid and not gas from glucose. 3. The aspect which at present 

 obtains of the varieties of " coliform " organisms is an aspect determined 

 by our media and its concomitants. 4. That atypical forms of " coli " 

 are not degenerate forms, but stages in the variation of organisms 

 belonging to the " coli-typhoid " group. 



Cultivation of Iron Bacteria. | — After a general account of the 

 researches carried out upon this group by various workers, particularly 

 JVIolisch and Ellis, since the time of his own investigations upon Crenothrix 

 polyspora in l'J07, W. Eullman describes his recent work upon the 

 cultivation of this organism. Upon agar and gelatin plates, to which 

 have been added iron or manganese in such forms as iron ammonium 

 citrate or nitrate, manganese peptone and other such substances, cultiva- 

 tions of Crenothrix have been obtained. Attempts to cultivate this 

 organism upon material derived from its natural source have had some 

 measure of success. Pure cultures have, however, not been obtained, 

 as contaminations with other iron bacteria, simple bacteria or aspergillus 

 have been encountered. 



* Centralbl. Bakt., Ite Abt. Orig., Ixii. (1912) pp. 536-7. 

 t Centralbl. Bakt., 2'e Abt., xxxiii. (1912) pp. 407-23. 

 X Centralbl. Bakt., 2te Abt., xxx. (1912) pp. 277-89. 



June mil, 1912 2 C 



