METHODS OF STUDYING H^MOLYSINS. 341 



two determinations, namely, one carried out with the single-solvent 

 dose of amboceptor, the other with a high multiple of the same. 

 The reasons for this procedure can be found in the study on the 

 quantitative estimation of amboceptor, complement, and anticom- 

 plement (page 250). 



So far as the estimation of the amount of amboceptor is concerned, 

 this is effected according to similar principles, and usually in such a 

 way that one works with an excess of complement. A certain diffi- 

 culty is encountered in the fact that the amount of complement 

 contained in the serum, e.g., rabbit serum, is variable. It is there- 

 fore always necessary, in order to exclude this disturbing factor, to 

 first determine the activating value of the complementing serum 

 using a specimen of the immune serum in question as a standard 

 serum. Directly after this test by which the amount of complement 

 is strictly defined, the quantitative estimation of amboceptor in 

 the new serum must be undertaken. 



It is also important to estimate the amount of receptor present 

 in the red blood-cells: the measure of this is the binding of ambo- 

 ceptor. 



Erhlich and Morgenroth (see pages 72 et seq.) have demon- 

 strated that the binding capacity of red blood-cells varies to an 

 extraordinary degree. While in many combinations the blood-cells 

 combine with just that amount of amboceptor, which on the addi- 

 tion of suitable complement leads to their complete solution (ambo- 

 ceptor unit}, it was found that in numerous other cases the blood- 

 cells are able to take up as high as 100 single-solvent doses of ambo- 

 ceptor. Corresponding to the amboceptor unit, the receptor unit, 

 is that amount of receptor which combines with one amboceptor 

 unit (see page 254). The combining power of the erythrocytes is 

 determined by adding varying multiples of the amboceptor unit 

 to the blood-cells, centrifuging at the end of about an hour and then 

 allowing the various decanted fluids to act on fresh blood-cells in 

 the presence of sufficient complement. The degree of haemolysis 

 which occurs readily shows just how much amboceptor was still 

 completely bound. (See page 75 and the protocols on pages 98 

 and 99.) 1 



1 Concerning the extraordinarily large binding capacity of bacteria for agglu- 

 tinins and for amboceptors, see the interesting communication of Eisenberg 

 and Volk (Zeitsch. f. Hygiene, Vol. 80) and of Pfeiffer and Friedberger (Berl. 

 klin. Wochensch. 1902, No. 25.) 



