154 J. M. SHERMAN AND W. R. ALBUS 



'' Streptococcus lacticus agrees in morphological, cultural and 

 coagulative properties with pathogenic, fecal and sewage strep- 

 tococci." 



Certain morphological characters are emphasized by some 

 workers as differentiating the true lactic-acid organisms from 

 other streptococci. It is pointed out that the cells of the milk 

 streptococcus are usually elongated and also that the char- 

 acteristic grouping is in pairs and short chains rather than in 

 long chains such as are usually found in the true streptococci. 

 These points cannot be used as sufficient ground for differentia- 

 tion since it is well known that many cultures of the lactic-acid 

 bacteria appear as perfect cocci, and the formation of the long 

 chains is not uncommon. Further, the streptococci from patho- 

 logical sources are frequently of the short chain type. Chain 

 formation, cell size and cell shape are so greatly influenced by 

 the nature of the nutrient medium that distinctions based upon 

 them are bound to be of doubtful value. 



Hastings (1911) has called attention to the fact that the lactic- 

 acid organism when grown in litmus milk causes a complete 

 reduction of the litmus previous to the curdling of the milk. 

 This is not true of the streptococci in general with which, as a 

 rule, the action on litmus is more gradual and not so complete. 

 This character has been used by Hastings and his associates to 

 differentiate the true lactic-acid bacteria from other strepto- 

 cocci which occur in milk and cheese. Unless, however, this 

 test can be correlated with some other points of difference, we 

 would not be justified in accepting it alone as giving a firm basis 

 upon which to separate the different groups of milk streptococci. 



From the study of a large collection of streptococci isolated 

 from milk, infected udders, saliva and feces of cows, Rogers 

 and Dahlberg (1914) were able to show that the streptococci 

 of milk resemble those which are associated with mammitis in 

 cattle, and that the types occurring in the cows' mouths and 

 feces are present only in small numbers and are probably rela- 

 tively unimportant in milk. They further pointed out that the 

 streptococci from infected udders had the same physiological 

 characteristics as the well known Streptococcus pyogenes. It has 



