6 MASS. EXPERIMENT STATION BULLETIN 319 



A temporary alteration in cultural and antigenic properties of Staphylococcus 

 aureus was demonstrated by Abbot (1912). Pigment formation and proteolytic 

 action were increased, while the agglutinability was decreased. No modification 

 was observed in its pathogenicity, carbohydrate-splitting power and ability to 

 clot milk. 



Baerthlein (1912) isolated several coli-like organisms from the intestinal tract 

 which appeared colorless on Endo-agar, but formed red secondary colonies. 

 These mutants gave rise to further mutants which were characterized by their 

 colonial, cellular, and serological differences. Two colony types were detected: 

 the one a transparent type containing long, slender filaments, and the other 

 opaque containing short, plump bacilli. The opaque type appeared to be antigenic 

 but inagglutinable with homologous and heterologous antisera. 



From studies on strains isolated from excreta of suspected typhoid carriers 

 Penfold (1912) concluded that lactose mutation appears to be a common property 

 of many bacterial species, and that it has no specific differentiating value. The 

 power to vary quickly in respect to dulcitol fermentation appears to belong to 

 every strain of Bad. typhosutn. Furthermore, the inability to vary quickly in 

 respect to certain carbohydrates would appear to be as characteristic of certain 

 species as the power to vary. 



Eisenberg (1912) observed numerous colonial and cellular types in his study 

 of the cholera vibrio. 



Rowland (1914) also demonstrated variation in cellular forms of the plague 

 bacillus. He further observed that the virulence and immunizing power of this 

 organism can be greatly modified when cultivated in various culture media. 



Cole and Wright (1916) concluded that most of the variation observed in ordina- 

 ry cultures is due to selection of pre-existent biotypes by the investigator or by 

 the environment. Certain biotypes may be entirely lost if the process of selection 

 is complete, and the culture will not return to the original type, even when placed 

 again under normal conditions. If the selection process is incomplete, certain 

 biotypes become predominant and others become suppressed, so that the return 

 to normal conditions brings out the dormant types adapted to those conditions, 

 and the culture reveals its original characteristics. 



In 1917 Jordan made a comparative study of biochemical and agglutinative 

 properties of some members of the Salmonella group. He offered the following 

 conclusion: "Old stock cultures that have been in laboratory collections for 

 some years often show variations, irregularities, and departures from type. 

 Some give reactions, biochemical and agglutinative, that they did not give when 

 first isolated. On the other hand, some strains that apparently possessed unusual 

 fermentative reactions when first isolated later show conformity to type". 



Eisenberg (1918), in one of his series of papers on variation reported a large 

 number of strains in the coli-paratyphoid-dysentery group. He observed variation 

 in size, transparency and structure of colony, mucoid property, biochemical 

 activity, gelatin liquefaction, pigment production, and reducing power. The 

 coli-mutabile strains possessed the power to change suddenly. Dwarf colonies 

 were detected among typhoid, paratyphoid B, and dysentery strains, as well as 

 secondary colonies among the latter. 



A classical work on variation appeared in 1918 by Baerthlein, which included 

 an extensive study of colony variation and other characteristics in fourteen 

 bacterial species. He demonstrated numerous colony types and correlated other 

 important characteristics, such as cell morphology, slime and pigment production, 

 bit .chemical and serological reactions, and virulence. His observations greatly 

 added to the knowledge of bacterial variation. 



