iv.] ARTIFICIAL COMMA-BACILLI. 65 



(a) In broth. Faintly alkaline beef-broth, or broth to which 

 i per cent, of peptone is added and rendered faintly alkaline, 

 or meat-extract peptone (i large tin of Brand's meat-extract, 

 10 grms. of peptone in 1000 ccm. of distilled water made 

 faintly alkaline) are very good fluid media, and in them the 

 comma-bacilli multiply with great rapidity. A flask or test- 

 tube of these materials inoculated with the comma-bacilli 

 and kept in the incubator at 35-37 C. is already slightly 

 turbid in twenty-four hours, every drop contains multitudes 

 of single commas and S- sna P e d forms. After three to four 

 days the turbidity has greatly increased, and a slight powdery 

 precipitate is noticed. On the surface of the broth a thin 

 loose pellicle is noticed already after 2-3 days, this becomes 

 more complete as growth proceeds ; on shaking the tube the 

 pellicle easily breaks up into flakes or thin scales, many of 

 them remaining on the surface. The fluid remains thin, but 

 has distinctly changed its reaction, having become acid ; there 

 is no offensive smell, but rather a slight aromatic flavour: 

 The fluid cannot yet be considered exhausted, since even 

 after a week the turbidity remains unaltered, while the 

 precipitate increases. After about a fortnight the fluid 

 begins to clear, as it were in layers, beginning at the sur- 

 face and gradually extending to the depth. The precipitate 

 meanwhile increases, and the fluid becomes after the lapse 

 of weeks almost clear (in the upper part) to the unaided eye, 

 but on examining a droplet under the microscope moving 

 comma-bacilli, singly, but chiefly S~ sna P e( i anc ^ spiral 

 forms, can be easily detected. The precipitate, from its 

 first appearance, is made up of living comma-bacilli and of 

 the granular debris of dead ones ; in these the outline and 

 sheath can in many instances still be recognised, either with 

 or without granules ; besides these there are smaller and 

 larger clumps and masses of granular debris. 



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