The absorption of amboceptor by corpuscles is rapid, a considerable amount being absorbed in as short a period as fifteen seconds. In the sensitization of corpuscles, the amount of amboceptor absorbed by the different corpuscles is not uniform, the inequality depending on the time taken in obtaining an even distribution of the corpuscles through the diluted immune serum. Amboceptor absorption is apparently influenced by the concentration of the corpuscles, being more rapid with a 5 per cent. than with a 2 per cent. suspension, and thus the stronger concentration is more susceptible to inequality of sensitization from variations in the method of activation. In experimental work, it is of importance to obtain as equal a sensitization as possible. It is essential that in comparative titrations the same method of activation be employed in the several titrations, and where possible it is advisable that all the cells used be sensitized together in bulk. The results obtained in titrating hemolytic sera and complement depend to a considerable extent upon the evenness of sensitization of the corpuscles.