44 VARIATIONS IN MORPHOLOGY [ch. iv 



Rosenow (1912-13) describes a streptococcus which de- 

 veloped unusual morphological and cultural characters as the 

 result of growth in unheated milk. 



B. coli in ascitic fluid and in bile may assume diplococcic 

 form (Adami, Abbott and Nicholson, 1899). Jenner (1898) 

 found that B. coli isolated from water was less thick and 

 opaque than normal B. coli, this distinction disappearing, 

 however, after growth in milk. 



Changes in the reaction of the medium may bring about 

 changes in morphology, bacilli giving place to cocci and diplo- 

 cocci and vice versa (Adami, 1892). 



5. The addition to the medium of various chemical sub- 

 stances influences morphology. The presence oiurea converts 

 Micrococcus prodigiosus into a bacillus (Wilson, 1906), and 

 Bacillus Pestis into a coccus grouped singly or in pairs or in 

 short chains (ibid.). B. enteritidis Gaertner on urine-agar 

 develops into a coccus {ibid.), while B. typhosus and B. 

 pyocyancus grown in carbolic acid (1 in 600), and creosote 

 (1 in 1000), assume the forms of non-motile cocci or diplococci 

 (Adami, 1892). 



Deceptive appearances are sometimes produced by the 

 unequal distribution of the staining material in an organism, 

 under conditions such as those we are discussing. A bacillus 

 may under the microscope appear to be a diplococcus and 

 a filament resemble closely a chain of cocci. 



Haslam (1898) found that the shape of B. coli communis 

 depended upon the composition of the medium in which it was 

 growing. If the composition of the medium were changed 

 every 24 or 48 hours the shape of the organism changed with 

 it. He found that the bacillus was longest (in proportion to 

 its breadth) in media rich in nitrogenous substances, such as 

 proteid and ammonium tartrate, and shortest in glucose media 

 to which little of such nitrogenous material had been added. 



6. Exposure to ultra violet rays in the case of B. anthracis 

 has been shown to change the bacilli to cocci and diplococci 

 (Henri, 1914). 



7. Electrolysis. Electrolysis may produce changes in the 

 morphology and staining properties of bacteria. Russ, for 



