STUDIES OX ILEMOLYSIXS. 77 



was employed did the centrifuged fluid contain a full solvent dose 

 and effect complete solution. Hence out of one hundred solvent 

 doses about ninety-nine had been bound by the blood-cells, for 

 only about one solvent dose of immune body remained in the fluid. 

 By means of parallel experiments we have found that one hour's 

 contact of immune body with blood-cells results in the maximum 

 amount of binding, for the experiments at 45 C. and room tem- 

 perature yielded results exactly alike. Between the extremes repre- 

 sented by these two experiments a great variety of figures was 

 obtained. 



The significance of these experiments offers no difficulties from 

 the point of view of the side-chain theory. The facts are readily 

 understood when we stop to consider the peculiarities of the receptor 

 apparatus of the blood-cells. As a result of our previous experiments 

 on the isolysins of goats we assume that a given blood-cell contains a 

 large number of different types of receptors which in general fit to 

 different immune bodies and haemo toxins. Referring the reader to 

 an exhaustive study by Ehrlich, 1 we shall content ourselves here 

 by remarking that certain kinds of receptors may be present in the 

 blood-cell in great excess. This excess cannot only be demonstrated, 

 but, by means of the method just described, can be exactly measured. 

 Entirely analogous conditions arise under other circumstances. 

 The interesting fact discovered by Wassermann, that the central 

 nervous system of various animals binds much more tetanus poison 

 in vitro than is necessary to fatally poison the animal, is probably 

 due to such an excess of receptors for tetanus poison. 



From this point of view the experiments above mentioned are 

 easily explained without departing from the side-chain theory. Thus, 

 let us assume that with a certain poison a it is necessary that x a-re- 

 ceptors are bound in order that a blood-cell be completely dissolved, 

 and let us further assume that the blood-cell posseses a much greater 

 number, say 2x a-receptor^. When Bordet's experiment is now 

 carried out, the conditions arising will be exactly those described 

 by Bordet. It is at once apparent that the red blood-cell in this 

 case will combine with just twice the amount of poison necessary 

 for its solution. If therefore double the solvent dose of immune 

 body is added to a given amount of such blood-cells, the entire receptor 



1 Specielle Pathologie und Therapie, edited by Xothnagel, Vol. VIII, sec- 

 tion 3, pages 163-184. 



