x] BACILLI: SPECIAL 185 



surface of Agar (streak) at 37° C. the growth is moist, sticky, 

 and grey. Broth is made uniformly turbid in twenty-four 

 hours; later on, an imperfect sort of pelHcle is noticed. Film 

 specimens (impression) made of young colonies on gelatine, 

 before liquefaction has set in, show beautiful filaments of 

 bacilli, some of considerable length and unsegmented, others 

 made up of short rods ; the filaments are straight or twisted 

 and at their ends show rapid division into cylindrical 

 bacilli. Fig. 56 shows such an impression film of the 

 swarmers of a young colony (sixteen hours old) ; Fig. 55 

 an impression of a colony twenty-four hours old, the centre 

 already liquefied. When the liquefaction has well pro- 

 gressed (say after two to three days) and a drop is examined 

 fresh under the microscope most of the bacilli are actively 

 motile, either short ovals — single or in dumb-bells — or cylin- 

 drical and even filamentous. There are also individuals so 

 short that they cannot be distinguished from cocci — single 

 cocci and diplococci ; and, further, some of the cylindrical 

 bacilli are more or less curved like vibrios, while some of 

 the filam^ents are wavy and even spiral-like. It is because 

 the microbe appears in such older cultures under all known 

 shapes {i.e. protean) that Hauser gave it the name of 

 " proteus.'' Proteus vulgaris is not, however, a single species. 



The liquefied gelatine and the broth cultures possess dis- 

 tinctly a putrid smell. The bacilli possess a single short 

 spiral flagellum, and it is astonishing how briskly they move 

 in the fresh state and therein stand in striking contrast with 

 some other bacilli, e.g. bacillus coli, which, though some 

 individuals are provided with several flagella, show only 

 very feeble movement in the fresh state. In some varieties 

 the bacilli possess quite a number of flagella. 



4. Proteus Zenkeri. — This is an aerobic, non-sporing, 

 motile bacillus of about o'4/* thickness and i to I'S/i length; 



