oG2 BACILLI OF NO KNOWN PATHOGENIC PEOPEETIES. 



described bacilli which undergo an extensive change of 

 form, and which always ultimately break up into cocci ; 

 but these observations evidently depended on contamina- 

 tion of the cultivations with other forms of bacteria, such 

 u contamination being almost unavoidable with the 

 methods of cultivation employed at that time. It is now 

 quite easy by the help of gelatine plates to isolate the 

 characteristic bacteria from any specimen of blue milk. 



Tbe bacilli move slow l v > fcne y llaYe an average length 

 of about 2 /*., but vary between 1'4 and 4 /*. ; their 

 thickness is about '4 ^., and in stained preparations it 

 also shows slight variations. In preparations from milk 

 their size is more uniform. At the ordinary temperature 

 spore formation occurs in gelatine, in milk, &c.; the spores 

 are formed at one end, so that the spore and the remains 

 of the bacillus often present a club form. In unsuitable 

 nutrient solutions, for example 

 in slightly acid solutions of tar- 

 f ammonia, or Cohn's nu- 

 trient solution to which nitrate 



Fig. 96.- Bacilli of blue ,, , . ,, , . , ,. 



milk x 700. of potasn is added, involution 



At a we see spore-bearing forms often appear, the bacilli 



bacilli, and others with > . 111 n ai 



unstained portions of being club-shaped or spmdle- 

 plasma - shaped, or presenting the form 



of long threads, with spherical dilatations at intervals. 

 Cultivations. In gelatine plates small greyish-white points appeal- 

 after two days, and these spread out on the surface in 

 the form of moist drops, 1 to 2 mm. in breadth. The 

 whole plate assumes a steel greyish-blue colour, so that 

 the white colonies become gradually more distinct. 

 Under low powers the smallest deeply-lying colonies 

 present the form of circular discs with black centre and 

 brownish granular margin, and with a sharp black 

 outline. The superficial colonies show a blackish- 

 brown centre, around this a greyish-brown area, and 

 further outwards a narrow, yellowish, finely granular 

 zone with sharp outline. In puncture cultivations a 

 whitish deposit is formed especially on the surface, and 

 from this growth a dark steel blue staining of the gelatine 

 spreads downwards. On potatoes a yellowish moist 



