L28 STUDIES l\ IMMUNITY. 



The bacteria are extremely numerous, normal as regards size and 

 color reaction, and arc present in short chains or as diplococci. 



n ,ond stage or the static of incomplete phagocytosis. — Twenty-two 

 hours after injection the number of bacteria is not very much 

 greater than at ten hours and phagocytosis is still incomplete 

 although leucocytes are numerous and the exudate less fluid. The 

 appearance of the bacteria in the fluid, however, remains the same. 

 They are. as a general thing, distinctly smaller and stain more faintly 

 with methylene blue. A large number of very small diplococci 

 are also found. There are to be noted also short chains composed 

 of very small cocci which are frequently compressed or unequally 

 spaced and often irregularly colored. More rarely still indistinct 

 chains, containing only a few stained cocci, appear. 



There are found scattered throughout the exudate well stained 

 normal chains with individual organisms as large or larger than 

 usual. 



There is a very distinct contrast between these normal or nearly 

 normal forms and the bacteria with the peculiar characteristics just 

 mentioned. In other words the streptococci, instead of being uni- 

 form in appearance, show distinct variations. 



Third stage or phagocytic stage. — 'Six hours later (that is 28 hours 

 after injection) there is generalized phagocytosis. 



The exudate has gradually become thicker, and contains a large 

 number of leucocytes of the polynuclear type and some mononu- 

 clear cells of variable sizes. It is to be noted that the mononuclears, 

 particularly the large macrophages, have distinctly outstripped the 

 microphages in phagocytic activity. Many of the microphages are 

 empty, whereas the mononuclear cells have taken up considerable 

 numbers of bacteria. On staining with Kuhne's blue it is found 

 that the phagocyted bacteria are generally the small ones taking 

 the faint stain and showing the peculiarities just mentioned. On 

 account of their smallness and their poor staining reaction it is 

 frequently difficult to detect them inside the phagocytes when 

 staining with methylene blue. This latter remark is applicable 

 to all instances of partial or total delayed phagocytosis; some cells, 

 to be sure, contain cocci of normal appearance that are easily 

 distinguishable in the cells, but the great majority of them occur 

 as small bluish indistinct points inside the cells. To demonstrate 



