ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 241 



corium only. All shades with the exception of red and pink are the 

 result of various combinations of these pigments ; orange-yellow and 

 black-brown. 



DifFerentiation of the Eberth-Coli G-roup by means of Collodion 

 Reagent Papers.* — A. Ch. Hollaude and J. Beauverie state that the 

 members of this group of organisms can be differentiated by means of 

 four test papers prepared as follows : — 1. Nitrate of silver paper. Filter 

 paper (e.g. Schleicher and Schiill) is soaked in 1 p.c. nitrate of silver 

 solution and is then dried rapidly l)etween two sheets of blotting-paper — 

 after drying, the paper is plunged into a mixture of alcohol and ether 

 containing 10 p.c. of pure collodion. The paper is then removed and 

 rapidly dried. 2. Glucose-neutral-red paper. The filter paper in this 

 case is plunged into a solution containing glucose 2'5 grm. in 25 c.cm. 

 of 1 p.c. aqueous solution of neutral red. This paper is dried and coated 

 with collodion as above. ;5. Acetate of lead paper. 10 p.c. aqueous 

 solution of acetate of lead is here employed, the rest of the technique 

 being as before. The paper, which is white in colour, should be kept 

 in a stoppered bottle. 4. Litmus-orcine -lactose paper. The solution in 

 which the filter paper is immersed is prepared as follows : — liitmus- 

 orcine 20 grm., neutral phosphate of sodium 4 grm., lactose 5 grm.,, 

 bicarbonate of sodium 1 grm., distilled water 50 c.cm. 



A portion of each of the four test papers is dropped into different 

 tubes containing 6 c.cm. of broth and then sterilized in the autoclave. 

 When cool the tubes are inoculated with the suspected organism and 

 incubated at o7° C. 



BadUus ti/phosus alone, after twenty-four hours, does not decolorize 

 the broth containing glucose -neutral-red paper, moreover the paper 

 remains at the bottom of the tube, and is not brought to the surface by 

 gas bubbles as with B. coli and the paratyphoid organisms. B. fara- 

 Ujphosm A does not blacken the acetate of lead paper, as do the other 

 organisms. B. paratyphosus B alone possesses the property of restoring 

 the lilac colour to the medium containing litmus-orcine-lactose, after 

 three days ; the other organisms permanently discolorize the medium. 

 B. coli alone gives a growth in the nitrate of silver medium, ten or 

 twelve liours after inoculation. 



By employing a paper made with a mixture of acetate of lead and 

 glucose neutral red the organism can be determined as follows : — With 

 B. typhosus the liquid remains red and the paper is blackened ; with 

 B. 'paratyphosus A the liquid is slightly reduced but the paper remains 

 red ; with B. paratyphosus B and B. roll the red colour completely 

 disappears and the paper is blackened. The red colour is replaced by 

 a yellowish fluorescence. 



* C.R. Soc. Biol. Paris, Ixxviii. (1915) pp. 722-5. 



