194 



MICRO-ORGANISMS AND DISEASE. 



The comma-bacillus of Koch is a curved rod of almost uniform 

 thickness, sometimes slightly pointed at the extremities, its 

 length about half that of a tubercle-bacillus, its thickness about 



' m 



? ,; 



y 



FIG. A. 



From a preparation of mucus flakes of the fluid in the ileum of a case of typical 

 cholera. Magnifying power about 700. Numbers of comma bacilli of 

 different lengths are shown amongst numbers of small straight bacilli. 



the same as that of the latter. But the comma-bacilli vary in 

 curvature and length within considerable limits, some being 

 just curved while others are almost semicircular, some being 



$ 



FIG. B. 



From an artificial cultivation of chole- 

 raic comma-bacilli in gelatine 

 peptone. Magnifying power 700. 

 Most of these are single curved 

 bacteria, a few are joined end to 

 end in twos, thus forming S-shaped 

 organisms ; and a few are in chains 

 of several placed end to end. 



J 



O 



Fid. c. 



From an artificial cultivation of chole- 

 raic comma-bacilli in Agar-Agar 

 peptone at the ordinary tempera- 

 ture of the room after several 

 weeks. The comma-bacilli change 

 by vacuolation into planconvex, 

 then biconvex, and finally circular 

 organisms ; these by division 

 give origin to two semicircular 

 comma-bacilli. Magnifying power 

 about 700. 



twice and three times as long as others. They are motile, and 

 divide transversly. In neutral Agar-Agar mixture, kept at ordi- 

 nary temperature, length-divisions may be observed, see Fig. c. 

 After transverse division they may remain joined end to end, 



