BY R. GREIG SMITH. 671 



The diminishing angle is a measure of the lack of staining 

 power, that is, of the intracorpuscular digestion. It is, however, 

 but a method of showing what was most clearly seen in the films; 

 the majority of the bacteria within the leucocytes were, in the 

 case of the three days' culture, imperfectly stained, and were 

 clearly in process of resolution. 



One more point seen in both of the experiments is the lower 

 phagocytic index of the bacteria in the three and four days' 

 cultures as compared with those of the two days'. This is probably 

 another illustration of the greater intracorpuscular digestion of 

 the older cultures and not an evidence of the formation of anti- 

 opsonins. An amplification of the last experiment was made in 

 order to see how still older cultures behaved. The results were 

 most irregular, and it appeared that ingestion and digestion were 

 occurring simultaneously and irregularly. 



Days 1 2 3 4 6 7 10 15 



Cocci per leucocyte ... 2*8 34 3*0 3'8 2*7 3*5 42 2*3 



The formation of auto-opsonins. — Old cultures of M. aureus, 

 whether in bouillon or on agar, are more translucent than young 

 cultures, and, as in the case of B. pyocyaneus, the translucence 

 may be due to the production of autodigestive ferments. Auto- 

 opsonins may also be secreted. To determine this point, an 

 experiment was made in which normal saline was used in place of 

 serum. 



Age of culture. Cocci per leucocyte. 



1 day 0-5 



2 days 0'7 



18 days 0'6 



22 days 1'7 



The result shows that no auto-opsonins are formed. 



The opsonic identity of races of M. aureus. — M. aureus has 

 been used throughout this series of researches because it is a 

 micro-organism that lends itself admirably to the purpose. Races 



