INFECTION AND IMMUNITY n 



kidney and bone; how the pneumococcus, which 

 rarely causes abscess of the lung, in which condi- 

 tions are somewhat similar to those within the pleural 

 cavity, may cause suppuration in other localities, 

 such as the middle ear, or in the subdural space, etc. 



In addition to the antibodies already mentioned, 

 the animal body produces agglutinins and precip- 

 itins directed against the invading bacteria, but 

 the relation of these antibodies to immunity is not 

 at all clear. Their production and identification 

 will be discussed in the following chapters. 



From what has been said it is evident that our 

 knowledge of the mechanism of immunity at least 

 so far as most infections are concerned is still very 

 obscure. Like most biological phenomena the deeper 

 we analyze the problem the more complex and 

 marvelous it becomes. 



