220 DISEASES DUE TO BACTERIA 



For the differentiation of the Bacillus typhosus, B. paratjphosus A 

 and B and B. coli four test papers are used as follows : — 



(i) A piece of filter paper is dipped into a i per cent, solution of 

 silver nitrate, and is then quickly dried; it is then dipped intO' 

 a lo per cent, solution of collodion in equal parts of alcohol 

 and ether, drained and dried in the dark. 



(2) A filter paper is dipped into a i per cent, solution of neutral red 



containing 10 per cent, glucose, and then dried and impreg- 

 nated with collodion as before. 



(3) A filter paper is dipped into a 10 per cent, solution of lead sub- 



acetic and dried, as before, with collodion. 



(4) A paper is dipped into the following solution : o'z grm. litmus,. 



4'o grm. neutral sodium phosphate, 5'o grm. lactose, I'o grm. 



sodium bicarbonate, 50 c.c. distilled water; it is then dried and' 



again treated Avith collodion. 

 Portions of these prepared papers are then dropped into peptone' 

 broth tubes, which are then autoclaved at 118° C. for twenty minutes. 

 Results. 

 (i) With the silver nitrate paper a growth of B. coli is obtained' 



in about twelve hours, of the three other bacteria in about two- 



to three days. 



(2) With the neutral red paper, the red colour of the paper and' 



broth are unchanged by B. typhosus, the paper remains at 

 the bottom of the tube, and there is no gas formation. 



With the three other organisms the colour changes to 

 canary-yellow, and gas is formed between the collodion and' 

 the paper, and the latter then flloats to the surface. 



(3) Lead acetate paper is blackened after about twentv hours, except 



in the case of B. paratyphosus A, in which no change occurs. 



(4) With the litmus lactose paper the lilac colour of the paper and 



broth is discharged after about twenty hours, but in three days 

 the colour returns in the case of B. paratyphosus B. 



In using hcprnocultures there are two methods : — 



(i) Dilution method. 



Take 2*5 c.c. of blood from the median basilic asepticallv, drop it 

 into a large sterile flask at once containing 200 to 300 c.c. of faintlv 

 alkaline broth. 



Incubate at 37° C. 



In twelve to twenty-four hours, in positive cases, the broth becomes- 

 cloudy and shows a germ growth. Then test this in various media. 



The agglutination test should also be done. 



(2) Bile enrichment method. 



Take blood as above or from the finger tip. 



