194 MICRO-ORGANISMS AND DISEASE [chap. 



like, or even spiral, but not very long. Bacillus coli grows 

 well in gelatine and broth to which phenol has been added 

 to the amount of 0-05 per cent. While these are in 

 general the characters of the typical bacillus, such as can 

 be isolated from stools normal and pathological, there occur 

 in the intestinal contents and discharges, as also in various 

 other substances — pathological secretions, dust, water, 

 sewage, &c. — bacilli which, examined as regards all the 

 above points, coincide in some, but differ in others. 

 Owing to their general morphological similarity — rods of 

 the shape and size of bacillus coh, and flagella, two to eight — 

 and owing to the non-liquefaction of gelatine and the power 

 to grow well in phenolated gelatine and broth, and the 

 identical appearances and rapidity of growth in gelatine 

 plates and in gelatine streak and stab, on Agar, potato, and 

 broth cultures, they must for the present be considered as 

 bacillus coli, but on account of their differing from the 

 typical bacilli in respect of gas-production in gelatine shake 

 culture, clotting of milk, and indol-reaction, they must be 

 considered as varieties of bacillus coli. (i) As to size, the 

 figures given above are open to considerable alterations, 

 since there are varieties of bacillus coli of which the 

 elementary rods as taken from a young colony on gelatine 

 or Agar appear distinctly and uniformly cylindrical, whereas 

 in some other varieties the great majority are under the 

 same conditions very short ovals. (2) As to motility, there 

 exist also great differences. While in some, e.g. the typical 

 bacillus coli of the intestine taken from a young colony, only 

 here and there a bacillus shows motility — darting to and 

 fro, and spinning round — there are varieties of which almost 

 all the bacilli, at any rate the majority, show active 

 motility. And similarly as to the number of flagella : for, 

 v/hile in some two or three flagella at one or both ends are 



