424 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



as well as certain mycobacteria, possess this property. The end pro- 

 ducts of this action on paraffin are carbon dioxide and water, but in- 

 termediate substances, such as acids and fatty acids, are formed. 



Isolation of Pathogenic Bacteria from Stools.* — W. R. Stokes and 

 F. "W. Hachtel recommend the following modification of Hesse's semi- 

 solid agar for the detection of typhoid and cholera organisms. It con- 

 tains : Agar 5*5 grm., Liebig's extract of beef 5 grm., Witte's peptone 

 10 grm., lactose 10 grm., glycerin 50 grm., sodium chloride 8" 5 grm., 

 distilled water 1000 c.cm. The beef extract is rendered sugar-free, by 

 preliminary inoculation of Bacillus coli. Before tubing, a solution of 

 Kahlbaum's azolitmin is added as indicator. Typhoid or paratyphoid 

 colonies are medium sized and of a pink colour. By using starch in place 

 of lactose and glycerin, the intestinal spirilla may be distinguished. By 

 virtue of their amylolytic enzyme, they split the starch and so produce 

 an acid reaction in the medium. 



Plate-culture of Anaerobic Bacteria.! — J. W. McLeod describes a 

 piece of apparatus for this purpose which possesses distinct advantages 

 over any of the older devices. It consists of two parts, a porcelain 

 dish to hold the pyrogallic acid and caustic soda solutions, and a special 

 Petri capsule, which has its free margin turned inwards and upwards. 

 The porcelain dish is a hollow chamber, bisected in the lower two- 

 thirds of its depth by a vertical partition, and there is a circular aper- 



FiG. 61. — Cross-section of the apparatus, to show the Petri dish 

 in position and bisecting the porcelain chamber in the line 

 of the partition. R, Groove to collect fluid exuding from 

 the medium on the Petri dish. P, Plasticine. X, Points 

 at which fluid in chamber passes over the partition when 

 the plate is tilted. 



ture in the centre of its upper surface. Around the margin of the 

 upper surface is a shallow groove filled with plasticine. In using the 

 apparatus, caustic soda and pyrogallic acid solutions are introduced into 

 the compartments of the hollow dish. The Petri plate is now pressed 



* Centralbl. Bakt., Ite Abt. Orig., Ixix. (1913) pp. 346-9. 

 t Journ. Path, and Bact.,xvii, (1918; pp. 454-7. 



