NATURE OF THE PROTECTIVE DEFENCES OF THE BODY 173 



according to Wright, but some, only, according to Neufeld. For many 

 infections, such as those due to the staphylococci, streptococci, and 

 piu'umococci, immunity seems to depend largely on the opsonines and 

 leukocytes. 



The opsonic power is measured by placing bacteria in a mixture of 

 the patient's serum and a saline emulsion of fresh white blood cells. 

 These are usually obtained from the fluid collecting after injecting an 

 aleuronat emulsion suspended in a thin starch paste into the pleural 

 cavity of a rabbit or other animal. The fluid is withdrawn twelve to 

 eighteen hours after the injection. In order to separate the leukocytes 

 from the pleural fluid they are washed in normal salt solution and 

 centrifugalized. We have found that suitable leukocytes can be 

 obtained very readily from the horse. The blood is received directly 

 into a flask containing some 10 per cent, solution of sodium citrate, 

 and in such amount as to make a 1 : 10 solution. This mixture does 

 not clot. The red cells sink to the bottom and the supernatant fluid 

 is centrifugalized. 



After placing at 37 C. for from fifteen to sixty minutes the average 

 number of bacteria taken up by the white corpuscles is determined by 

 examining stained preparations. Wright noticed that there was no 

 opsonic power in the fluid in an abscess cavity, and that even while the 

 blood as a whole might have it, that of some organ or portion of the 

 body might lack it. 



Deflection of the Complement. It frequently happens that when the 

 addition of a small amount of immune serum renders a normal serum 

 more bactericidal a greater addition robs it of all bactericidal power. 

 This is explained by Neisser and W T echsberg to be due to a locking up 

 of complement by excess of immune body. The subject is in need of 

 further study. 



Multipartial or Polyvalent Sera. According to Ehrlich's theory, every 

 immunizing group in a substance corresponds to a countergroup of the 

 fitting receptors in the organism. Bacteria are not homogeneous masses, 

 but are made up of various molecules which differ biologically from 

 one another. Conforming to this, the antisubstances, immune bodies 

 (antitoxins, agglutinins, etc.), which appear in a serum are made up 

 of the sum of the antibodies which correspond to these partial ele- 

 ments in the bacterial body. These separate groups are called "partial 

 groups." An immune serum, therefore, consists of the partial groups 

 which correspond to the separate partial elements of the bacterial body. 

 We are further able to show that these partial elements in one and the 

 same bacterial species are not the same for all the bacteria of that 

 species. Thus one culture of streptococci or of bacillus coli may have 

 a few partial elements which differ from those of another culture. 

 What is the consequence of this? The consequence will be that when 

 we immunize with a culture a of such bacteria we shall obtain a serum 

 which acts completely on this culture, for in this serum all the partial 

 elements present in culture a are represented. If, however, AVC employ 

 culture b, c, or <7, which perhaps possess other partial elements, we 



