STUDY OF ANTISTREPTOCOCCUS SERUM. 129 



phagocytosis well boracic carmine followed by Gram's stain should 

 be used.* 



Fourth stage. Post phagocytic stage or stage of reinfection. 

 Preparations from the exudate 34 hours after injection still show 

 a few small unphagocyted bacteria, but whereas these organisms 

 are in relatively small numbers, the number of well stained, plump 

 and normal appearing chains is considerably increased. That is 

 to say this latter form of the streptococcus has increased propor- 

 tionately over the other. New streptococci have been formed by 

 the multiplication of the normal appearing organisms that have 

 resisted engulfing. The animal dies shortly after, say 40 hours after 

 inoculation. 



A few scattered streptococci in short chains and normal in 

 appearance are found in the blood, as is usual at the time of death 

 in rabbits injected with serum. 



This description of a peritoneal infection characterized by a 

 partial phagocytosis naturally varies considerably. The duration 

 of the different stages may vary and the relative proportion of 

 the normal and abnormal bacteria before phagacytosis may also 

 change.f 



Sometimes the animal, being exhausted, dies at the beginning of 

 a phagocytosis that concerns only a small proportion of the bac- 

 teria present in the exudate. But one observation is constant, 

 namely, a peculiar appearance of the bacteria at the moment when 

 phagocytosis begins; this peculiarity of faint staining and small- 

 ness which is found in the majority of bacteria that are being taken 

 up by phagocytes is shown best by staining with methylene blue. 



* Staining bacteria with gentian violet followed by Gram's stain and decolori- 

 zation with alcohol and clove oil is not always satisfactory. It stains bacteria 

 rather violently and does not bring out the differences between individual strep- 

 tococci. To bring out clearly details in the appearance of bacteria a more delicate 

 stain like Kiihne's blue is necessary. 



The normal appearing chains already mentioned are rarely to be found within 

 cells. They remain extracellular and are somewhat increased in number, whereas 

 the number of altered bacteria has greatly decreased outside the cells owing to 

 phagocytosis. 



t Partial phagocytosis can appear only relatively late. For example, we have 

 seen a partial phagocytosis appear after nearly 48 hours. But even in this 

 instance the exudate was full of leucocytes at 12 hours and later became purulent. 

 Such cases prove the extreme persistence of the negative chemiotaxis of the 

 micro-organism. 



