CH. I] THE SCOPE OF THE ENQUIRY 11 



The acquirement of power to ferment a certain carbo- 

 hydrate may coincide with the loss of fermenting power in 

 other directions. 



Penfold (1910-11) has shown that the development of new 

 fermenting powers on the part of B. typhosus towards lactose 

 and dulcite is frequently associated with the formation of 

 papillae on its colonies. Diminished gas-production in glucose 

 media on the part of certain coliform organisms {B. (xrunthal, 

 etc.) was likewise associated with papillae formation. 



The same observer found that colonies of B. typhosus which 

 had lost the property of fermenting glycerine showed impaired 

 agglutinability also, though typical fermenting colonies on 

 the same plate were normal as regards agglutination. 



Adami, Abbott and Nicholson (1899) found that the as- 

 sumption of coccic and diplococcic forms by B. coli in the 

 organs of healthy animals was associated with a loss of power 

 to ferment carbohydrates and to produce indol. 



Gordon (1900-1) observed that the tendency of the strep- 

 tococcus of scarlet fever to assume a bacillary form was 

 abolished by "passage" and at the same time its virulence 

 was increased. 



Rosenow (1914) obtained a strain of streptococci from the 

 throat in a case of scarlet fever, which yielded on blood agar 

 two distinct kinds of colonies. These displayed marked differ- 

 ences in their fermenting power and also in their pathogenicity. 



Many other instances might be given. 



3. The development of intermediate forms, i.e. the possible 

 derivation from one or other of two known species of forms 

 intermediate between them in their characters. For example, 

 W. J. Wilson obtained from the urine of a supposed typhoid 

 carrier (1910), and also from the urine in certain cases of 

 cystitis and pyelitis (1908), coliform organisms intermediate 

 in their characters between B. typhosus and B. coli communis 

 and derived presumably from B. typhosus in one case and 

 from B. coli in the others. Many other observers have 

 described organisms resembling both B. typhosus and B. coli 

 communis in their characters, Klotz (1906) has described 

 such an organism, isolated from water, and called by him 

 Bacillus perturbans. Mcnaught (1905) described two varieties, 



