THE COLON -TYPHOID GROUP 107 



The faeces are first diluted by emulsifying 1 or 2 

 grammes of fcecal matter with about 700 c.c. of sterile 

 normal salt solution; when the emulsion has stood for 

 about one hour, so as to allow the coarser particles to 

 subside, a small quantity of the supernatant fluid is 

 pipetted off for plating. It is necessary to use three large 

 Petri dishes for each case; about four drops of the fluid 

 emulsion is transferred to plate 1, and carefully spread 

 over the surface with a glass rod spreader bent at right 

 angles. The same spreader, but without being reinfected, 

 is then carefully rubbed in succession over the surface of 

 plates 2 and 3; all three plates are then incubated at a 

 temperature of 37 C. for twenty-four hours. 



Colonies resembling typhoid or paratyphoid are worked 

 up. 



To inhibit B. coli, some workers make a primary 

 inoculation of fseces into peptone water every 5 c.c. of 

 which contains - 2 c.c. of a 1 in 10,000 solution of brilliant 

 green, incubate for one or two days and then plate out. 

 The simple plating is, however, quite satisfactory. 



With urine it is only necessary to spread a small quan- 

 tity, varying from a few drops to 1 c.c. or thereabouts, 

 over the surface of a plate containing one of the media 

 mentioned, and then to proceed as above. 



The Dysentery Bacillus. 



The several varieties of dysentery are due to different 

 etiological agents. In one form the tropical or amoebic 

 an amoeba is believed to be the causative organism 

 (see p. 174); in a second form, the so-called epidemic or 

 bacillary, a bacillus (B. dysentericc:} is the infecting agent. 

 The paratyphoid bacilli and B. pyocyaneus may also 

 cause a dysenteric condition, and possibly other organisms 

 e.g., the B. coli and Proteus vulgaris and certain 

 parasites e. g., the bilharzia produce a pseudo-dysen- 

 tery. 



As many as fifteen types of dysentery bacilli are said 

 to exist, the Shiga-Kruse and the Flexner groups being 

 best known. 



Morphology. The dysentery bacilli form no spores 

 and are Cram-negative. They are generally said to be 

 non-motile, and most workers have failed to demonstrate 

 flagella. 



