INTRODUCTORY 7 



Quantitative Relations of Antigen and Anti-substance. 

 The haemolytic dose of immune-body is sometimes extra- 

 ordinarily small. In other words, the amount of immune- 

 body as judged by the proportionate number of molecules 

 appears to be very great. It is now recognized that 

 the amount of anti-substance developed may greatly 

 exceed the combining equivalent of antigen injected. 

 This fact, which is of great importance in connexion 

 with the general question as to the production of anti- 

 substances, is well illustrated in the case of hsemolytic 

 serum. For example, after the injection by the intraperi- 

 toneal method of the corpuscles of 30 c.c. of ox's blood, on 

 several occasions a serum was obtained of which -0005 c.c. 

 was the haemolytic dose for 1 c.c. of a 5 per cent, suspension 

 of ox corpuscles ; that is, -01 c.c. was the dose for 1 c.c. 

 of undiluted blood, or 1 c.c. haemolytic serum would dissolve 

 completely 100 c.c. of ox's blood. Taking the total amount 

 of the haemolytic serum in the animal as 60 c.c., we find 

 that the anti-serum would dissolve 6000 c.c. of the ox's 

 blood. The red corpuscles in question, however, have the 

 faculty of combining with several haemolytic doses, although 

 it is not possible to say exactly how many. Even when this 

 allowance is made, the anti-serum would satisfy the com- 

 bining affinities of several hundred cubic centimetres of 

 ox's blood. In other words, the antigens of the corpuscles 

 injected give rise to the production of many times as much 

 anti-substance (immune-body) as would satisfy the com- 

 bining affinities of the total amount of antigens used. 



