Bacillus Proteus Vulgaris 335 



ever putrefactive change is in progress. It is a common mistake for 

 the novice to look upon it as a member of the Bacillus coli group. 

 Morphology. — The bacilH are variable in size and shape — pleo- 

 morphic — and are named proteus from this peculiarity. Some differ 

 very little from cocci, some are more like the colon bacillus in shape, 

 others form long filaments, and occasional spirulina forms are met 

 with. True spirals are never found. All of the forms mentioned 

 may be found in pure cultures of the same organism. The diameter 

 of the bacillus is usually about 0.6 n, but the length varies from 1.2 

 jLt or less to 4 M or more. No spores are formed. The organisms are 

 actively motile. The long filaments frequently form loops and 

 tangles. Flagella are present in large numbers. Upon one of the 



Fig. ii2.^Bacillus proteus, showing flagella (Migula). 



long bacilh as many as one hundred have been counted. Involution 

 forms are frequent in old cultures. 



Staining.^ — The bacilH stain well by the ordinary methods but not 

 by Gram's method. 



Cultivation.^ — The proteus is easily cultivated and grows well in 

 all the artificial media. 



Colonies.^ — Upon gelatin plates a tj^ical phenomenon is observed 

 in connection with the development of the colonies, for the most 

 advantageous observation of which the medium used for making 

 the cultures should contain 5 instead of 10 per cent, of gelatin. 

 Krusef describes the phenomenon as follows: . 



"At the temperature of the room, rounded, saucer-shaped depressions, with 

 a whitish central mass surrounded by a lighter zone, are quickly formed. _ Under 

 low magnification the center of each is seen to be surrounded by radiations ex- 

 tending in all directions into the solid gelatin, and made up of chains of bacilli. 

 Between the radiations and thfe granular center bacteria are seen in active motion. 

 Upon the surface the colony extends as a thin patch, consis1,jng of a layer of 

 bacilli arranged in threads, sending numerous projections from the periphery. 



* Flugge's "Die Mikroorganismen." 



