A STUDY OF SPONTANEOUS AGGLUTINATION 79 



tination. When these were sub-cultured at later periods, the 

 colonies showed both agglutinating and non-agglutinating tjqies. 

 In all instances the changes in the strain was from a pure to 

 two types of colonies. The results of this work indicate that 

 every member of the colon-typhoid group is changeable and 

 may develop two types of colonies, dependent upon duration 

 of cultivation or other circumstances of growth, as well as upon 

 the type of artificial culture medium employed. 



PHENOMENA OF SPONTANEOUS AGGLUTINATION IN VARIOUS FLUID 

 CULTURE MEDIA (TABLE 4) 



It has been observed, that spontaneous agglutination may 

 occur in all ordinary fluid or solid culture media. Spontaneous 

 agglutination occurs in a greater degree in glycerol broth, pep- 

 ton water and all acid media, than it does in neutral or alkaline 

 broth and it is more marked in concentrated than in dilute, 

 Uquid pepton medium. Cultures in alkaline broth usually 

 remain clear and transparent, the presence of the alkali greatly 

 retarding or completely inhibiting spontaneous agglutination. 



When glucose broth was used as a culture medium, spontan- 

 eous agglutination of Bad. typhosum was prevented in many 

 instances, but glucose broth cultures of Bad. paratyphosum A 

 and B showed spontaneous agglutination in 24 hour cultures, 

 and this has been even more marked with similar cultures of 

 Bad. coli. 



Growth in plain broth, either weakly acid or neutral in reac- 

 tion, depends upon the type of colony. In some instances there 

 is an excessive growth as well as a spontaneous agglutination. 

 When such a culture was shaken or mixed with broth or salt 

 solution, it disintegrated being thus differentiated from true 

 spontaneous agglutination, in which disintegration occurs only 

 when special methods are employed. 



Plain broth or pepton water cultures which became spontan- 

 eously agglutinated were at first clear and after twenty-four 

 hours a sediment was forming. If a cloudy growth is encountered 

 in sub-culture, we are sure to find both spontaneous and non- 

 spontaneous agglutination tyi)es of organisms present. This 



