BY H. G. CHAPMAN. 



547 



The readings show that the combined precipitates with the 

 heterologous protein did not equal the precipitate with the 

 homologous protein. 



Table xvi. 



Another method of differentiation of closely related proteins 

 has been described b}' Welsh and Chapman.* This method 

 depends on the inhibition of the formation of precipitate by 

 heated antisera, i.e., on the solution of precipitate by heated 

 antisera. It is not, however, so simple as that described above, 

 as it involves a thorough knowledge of the inhibitory powers of 

 the antisera employed, and requires a detailed examination of 

 each antiserum before use. The results obtained in the research 

 on crossed inhibition led Welsh and Chapman to suggest that 

 the precipitate given by hen-egg antiserum and ostrich or any 

 egg albumen other than hen-egg albumen might be regarded as 

 similar to that produced by ostrich-egg antiserum and any egg 

 albumen other than ostrich-egg albumen. It could be assumed 

 that this precipitate resulted from the general avian character or 

 component of the proteins used in immunisation, while the greatly 

 increased precipitate produced by hen-egg albumen and hen-egg 

 antiserum, or by ostrich-egg albumen and ostrich-egg antiserum 

 could be assumed to be due to the specific hen or ostrich char- 

 acter or component of the material used for injection. In this 

 connection, some observations made on the eggs used for the 

 experiment recoi'ded in Tables xiv. and xv., may be noted. After 



* The principles of this method are outlined by Welsh and Chapman, 

 Proc. Roy. Soc. London, B.79, p.471, 1907. 



