92 Chapter IV 



tributes the interesting fact that the sensibilising substance is found 

 even in great excess in the serum of treated animals. When he adds 

 to this serum blood that has not been heated, he produces a haemo- 

 lysis that is more than thirty times as active as when the serum of 

 the prepared animal alone is used. From the quantitative point of 

 view, then, there is no relation between the amount of the two sub- 

 stances in the serum of prepared animals. 



It may be suggested that the sensibilising or intermediary sub- 

 stance is the same as that which produces the agglutination of the 

 red corpuscles. But careful researches have thoroughly demonstrated 

 the difference between the two substances that have this character in 

 common, both resist heating to 55 60 C. and even beyond this point. 



Having established this co-operation of two substances in haemo- 

 lysis the intimate mechanism of their action was next studied. Here 

 I must give pride of place to the discovery by Ehrlich and Morgenroth 

 that the intermediary (or sensibilising) substance links itself to its 

 corresponding red corpuscles. A serum, capable of dissolving the 

 red corpuscles of a different species, is heated to 56 C. which causes 

 it to lose this solvent property. When a certain number of these 

 corpuscles are added to it, such corpuscles remain intact although 

 they are agglutinated. It is sufficient, after some hours of contact, to 

 centrifugalise the mixture in order to separate a limpid serum from 

 the mass of red corpuscles, the former being now entirely deprived of 

 its intermediary substance, that is to say it has become incapable of 

 dissolving the red corpuscles even with the addition of a large quantity 

 of the " complement " (normal serum, unheated). On the other hand, 

 the red corpuscles, having fixed (linked) all the intermediary sub- 

 stance, dissolve very rapidly when placed in contact with normal 

 serum which contains the necessary quantity of the complement (or 

 alexine). This fundamental experiment has been confirmed and 

 repeated by many observers and has now become classic. The idea 

 that the intermediary (or sensibilising) substance links itself to the 

 red corpuscle, without dissolving it, is generally accepted and may be 

 regarded as permanently settled. We should do well, then, instead 

 [99] of designating by all sorts of synonyms the substance 'in serums which 

 resists the action of a temperature of 55 65 C., to apply to it, once 

 for all, the name of fixative substance or simply that of fixative. 

 This name is short, expresses the essential character of the substance 

 and gives rise to no misunderstanding, as do the other names proposed 

 up to the present (amongst them that of philocytase employed by 

 myself in some of my earlier publications). 



