Resorption of the formed elements 89 



(horse). Continuing their researches in this direction, Ehrlich and 

 Morgenroth have come to the conclusion that the normal serum of a 

 single species may contain several intermediary substances, each one 

 acting on a single species of red blood corpuscles. Further, that 

 normal serum must contain several or even many different comple- 

 ments. 



Ehrlich and Morgenroth carried on researches on the intermediary 

 substances in normal serums and found several in addition to that 

 already mentioned. The serum of the normal dog readily dissolves 

 the red blood corpuscles of the guinea-pig. When heated to 57 C. it 

 loses this property; but with the addition of normal guinea-pig's serum 

 the property is regained. In the serum of the normal dog there exists, 

 then, besides the complement, at least one intermediary substance. 

 The same result can be obtained with several combinations of serums 

 of normal mammals, heated or unaltered 1 . Yet it often happens, as 

 Ehrlich and Morgenroth themselves point out, that the demonstration 

 of the presence of the intermediary substance in normal serums is 

 accompanied with marked difficulties. Bordet, also, who has studied 

 this question very thoroughly, often failed completely in his attempts 

 to make normal serums, that were incapable of producing haemolysis, 

 active by the addition of heated serums of other species of animals. 

 Thus he observed that normal fowl's serum readily dissolves the red 

 corpuscles of the rabbit When heated to 55 56 C. this serum 

 loses its haemolytic power which cannot be restored by the addition 

 of any normal serum. He thinks therefore that, in this example, 

 haemolysis is produced solely by the alexine, without the assistance 

 of any intermediary substance in the serum of the normal fowl. 

 P. Miiller 2 , whilst confirming Bordet's experimental results, considers 

 that, in this case also, there is the intervention of an intermediary 

 substance. When he mixed heated fowl's serum with a small quantity 

 of unaltered fowl's serum the solution of the red corpuscles of the [96] 

 rabbit is not brought about. When, however, instead of adding a 

 little imheated normal fowl's serum, he added the same quantity of 



1 Ehrlich and Morgenroth, " Ueber Haemolysine," II, Berl. klin. Wchnschr., 1899, 

 S. 481. The following are the combinations found by these observers : heated calf's 

 serum with normal serum dissolves the red blood corpuscles of the guinea-pig; 

 heated rabbit's serum plus sheep's serum dissolves the red blood corpuscles of the 

 sheep ; heated serum of rabbit with the addition of goat's serum dissolves the 

 red corpuscles of the goat ; heated sheep's serum with guinea-pig's serum produces 

 haemolysis of the red corpuscles of the guinea-pig. 



2 CentralU.f. Bakteriol u. Parasitenk., i te Abt, Jena, 1901, Bd. xxix, S. 175. 



