'II- 



$76 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the method as suggested by different workers, which depend on the 

 variations in the nature or composition of the media employed. He- 

 contrasts the media of Rothberger and Oldenkop with media prepared 

 with ordinary broth and gelatin to which neutral red in similar amounts 

 has been added. The details of his observations on 80 different strains 

 of organisms, mostly belonging to the Coll group, are given in tabular 

 form. From these results he concludes that the neutral red reaction is 

 best obtained by [the use of ordinary laboratory gelatin with the 

 addition of sterilised, saturated, aqueous solution of neutral red, and 

 incubating at 37° C. ; under these circumstances he finds that the 

 reaction appears quickly within G hours, is uniform and reliable, and 

 remains permanent, being influenced neither by the medium nor by the 

 oxygen of the air. 



Methods for Isolating the Micro-organisms of Nitrification.*— 

 R. Perotti uses blocks of commercial carbonate of magnesium, which 

 are sawn up into slices about 10 cm. long, 2 -5 cm. broad, and 1 cm. 

 thick. Of course any other size or shape will do. The slices are first 

 polished with glass, and afterwards rubbed down quite smooth with the 

 finger. 



The nutritive medium is composed of three solutions. (1) Ammonium 

 sulphate, 2 grm. ; potassium phosphate, 1 grm. ; magnesium sulphate, 

 0-5 grm. ; distilled water, 1000 grm. (2) Sulphate of iron, 2 grm.; 

 distilled water, 100 grm. (3) Saturated solution of sodium chloride. 

 To 50 c.cm. of (1) are added one drop of both (2) and (3). The solution 

 must be made fresh when required for use. 



The magnesium carbonate slab is placed in a tube, and then as much, 

 of the medium poured in as will suffice to soak the block and allow a 

 deposit of from 5-10 c.cm. at the bottom of the tube. The whole is. 

 then steam-sterilised. 



It is important to have some of the medium at the bottom of the 

 tube for the purpose of keeping the slab moist. 



The surface of the block is inoculated by running over it a few 

 drops of the fluid containing the micro-organisms. 



The presence of the organisms is detected by the appearance of 

 minute excavations of a dirty yellow hue on the surface of the medium. 



Bndo's Method for Detecting Typhoid Bacilli.f — The medium 

 devised by S. Endo is composed of the following ingredients : — 100O 

 c.cm. neutralised nutrient agar (3 p.c. agar) ; 10 grm. chemically pure 

 lactose ; 5 c.cm. alcoholic solution of fuchsin ; 25 c.cm. 10 p.c. sodium 

 sulphite solution ; 10 c.cm. 10 p.c. soda solution. 



The medium is prepared as follows : — 500 grm. of chopped beef„ 

 1 litre of water, 10 grm. of pepton, 5 grm. of salts, and 30 grm. of 

 agar are well boiled, filtered, neutralised, and alkalinised by the addition 

 of 10 p.c. soda solution. 



The lactose and fuchsin solution are then added. This makes the 

 medium red, but after the addition of the sodium sulphite it gradually 

 loses colour, and when the agar is set it is quite colourless. 



* Atti R. Accad. Lincei, xiv. (1905) pp. 22S-31 (1 fig.), 

 t Centralbl. Bakt, 1* Abt. Orig., xxxv. (1903) pp. 109-10. 



