SHERWOOD: PLEOMORPHIC STREPTOCOCCI. 251 



uniform chain formation under partial anerobic conditions, it was 

 decided to try increasing the oxygen tension slightly above at- 

 mospheric and see if this had any effect upon involution. This 

 gave unsatisfactory results, as well as an experiment in which the 

 COo content of the atmosphere in contact with the culture media 

 was varied. These negative results naturally do not mean that 

 these involutions can not be controlled, as no doubt that time and 

 patience or good fortune would yield positive results. I might 

 say, however, that some of my work on another problem has sug- 

 gested that perhaps the pleomorphism on the partially desiccated 

 agar was due to the salts that crystallized out on the surface of the 

 agar. It is hoped that this may be checked up more fully in the 

 future. 



Even if involution forms could be produced at will under one 

 set of conditions, it would not necessarily follow that these were 

 the conditions holding forth in the body under which pleomor- 

 phism occurred or persisted. The variation of the morphology of 

 these organisms from typical streptococci have been termed in- 

 volution forms, largely because (1) these organisms seem to prefer, 

 as a rule, to grow and act as streptococci under artificial conditions 

 of laboratory cultures; (2) the streptococci as a group is knowTi to 

 be very plastic, mutations occurring in many different ways; 

 (3) similar though more transient variations in morphology have 

 been observed to occur in pure cultures of streptococci; (4) since 

 sufficient evidence is not apparent to change the classification 

 given them by Kurth, Gordon and Klein. 



The similarity to B. diphtheria noted by Gordon and empha- 

 sized by Newman is at times quite striking. Not enough strains 

 of these organisms were studied to warrant a statement that none 

 might contain metachromatic granules, since it is a well-known 

 fact, as emphasized by Graham Smith, ^^ that not all strains of 

 virulent B. diphtheria have metachromatic granules. None were 

 observed in the cultures studied. I know that frequently these 

 pleomorphic streptococci may be mistaken for B. diphtheria when 

 smear preparations only are examined. A bacteriologist experi- 

 enced in diphtheria examinations would not make the mistakes, 

 but when one realizes that many relatively inexperienced indi- 

 viduals make throat examinations, either for themselves or others, 

 it is quite possible for errors to be made. These errors would be 

 upon the positive side and might or might not be objectionable, 

 depending upon the tolerance of the individual for the foreign 

 protein, any benefit derived from it, the expense incident thereto. 



