specificity. The possibility of doubly or trebly specific 

 globulin molecules cannot however be wholly dismissed. 



In general, the problem of antibody production is to 

 determine how a series of globulin molecules are related to 

 the antigenic determinants with which they react. It will be 

 characteristic of my personal approach that the physical 

 relationship will be dismissed as a pair of complementary 

 configurations and taken for granted. The relation that will 

 interest us is how a large population of appropriately 

 patterned globulin molecules is called into existence by the 

 entry of antigen into the body. 



Antigen molecule Antibody population 



©0© 

 ©©^©„ 



®©®0§® 



Fig. 4. Schematic representation of an antigen molecule and the anti- 

 body population in a corresponding antiserum. Note that of the large 

 number of potential antigenic determinants only those not represented 

 in the components of the reacting animal are active. 



2. Differences between primary and secondary response 



If we take any ' good ' antigen, either soluble or particulate, 

 for which we have a convenient in vitro method of titrating 

 the corresponding antibody and inoculate a series of animals, 

 it will usually be a simple matter to show the characteristic 

 difference between primary and secondary response. A par- 

 ticularly clear example is that obtained with staphylococcal 

 toxoid in early work (Burnet, 1940), where the primary 

 response is slow and of low titre, the secondary one rapid and 

 rising almost logarithmically to a higher titre. 



31 



