ANAPHYLAXIS 269 



6. It is possible that in natural immunity there might 

 be no receptors in the body cells to take up the organisms 

 or their products, or the receptors might be present in 

 certain cells but of a very low chemical affinity, so that com- 

 bination does not occur. It is even highly probable that 

 many substances formed by invading organisms which might 

 injure specialized cells, such as those of glandular, nervous 

 or muscle tissue, have a more rapid rate of reaction with, or 

 a stronger affinity for, lower unspecialized cells, such as con- 

 nective and lymphoid tissue, and unite with these so that 

 their effects are not noticed. 



The importance of these different factors varies in differ- 

 ent diseases and need not be considered in this connection. 



The question "which of the body cells are engaged in the 

 production of antibodies" is not uncommonly asked. On 

 physiological grounds it would not seem reasonable that the 

 highly specialized tissues above mentioned could take up 

 this work, even though they are the ones which suffer the 

 greatest injury in disease. Hence it is to be expected that 

 the lower or unspecialized cells are the source, and it has 

 been shown that the antibodies are produced by the phago- 

 cytes (though not entirely as Metchnikoff maintained), by 

 lymphoid tissue generally, by the bone marrow and also by 

 connective-tissue cells, though in varying degrees. 



Since immunity depends on the activity of the body cells 

 it is evident that one of the very best methods for avoiding 

 infectious diseases is to keep these cells up to their highest 

 state of efficiency, to keep in "good health." Hence good 

 health means not on\y freedom from disease but also protection 

 against disease. 



