An Experimental Enquiry into the Relationship of Leucocytosis 

 to the Opsonic content of the Blood Serum, 



I. — Introduction. 



The following experiments were undertaken with a view to determine 

 whether and to what extent the opsonic content of the blood serum, 

 towards various micro-organisms, is influenced by changes in the number 

 and character of the circulating leucocytes. The general association of 

 leucocytosis with natural and experimental bacterial infection, has long 

 been observed as a more or less constant phenomenon, without any very 

 exact conclusions having been reached regarding the precise role played 

 by such leucocytic variations. 



It is obvious that this response on the part of the white cells to 

 infection of the organism, must form a very important link in the chain 

 of protective mechanisms called into play by the animal body, but, where 

 opinions have differed and still differ, is in the interpretation of the 

 comparative rdles played by the cellular elements and the surrounding 

 fluid medium, and in the rationale of their inter-dependence, if such 

 exists. 



It has been shown by Wright and Douglas (i) and Bulloch and 

 Atkin (2) that in comparing in vitro the opsonic content towards micro- 

 organisms, of normal with pathological sera, the variant is the serum, 

 while the leucocyte may be regarded as a more or less indifferent factor : 

 that is to say, normal leucocytes may be employed instead of those 

 corresponding to the serum to be tested, without incurring any 

 appreciable error. 



It may here be observed, however, that in certain diseases of the 

 haemopoietic system, one of us (Ledingham) has put on record evidence 



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