128 THE LYSINS. 



goats used in the second experiment contained both thermo-labile and 

 thermo-stable addiments. 



Another experiment showed that the blood serum of a non-treated 

 normal animal dissolved the erythrocytes of the guinea-pig and that 

 there is in the normal serum of the goat a substance analogous to the 

 immune body found in immunized animals, which combines with the 

 corpuscles of the guinearpig at 0°. It is evident from this that the 

 term " immune body " is not appropriate for the substance which 

 combines with the erythrocytes at 0° and which is one of the hemo- 

 lytic factors. This led Ehrlich to substitute for the term " immune 

 body " the designation of " intermediary body," ' and inasmuch as 

 he had demonstrated that there might be different addiments in the 

 blood, he also dropped this term and used in its stead "comple- 

 ment." It should be understood that the " immune body," which 

 we will hereafter designate as " intermediary body," has two hap- 

 tophorous groups, one of which is possessed of great avidity, and it is 

 by means of this that the intermediary body combines with the cor- 

 puscles, and its great avidity is shown by the fact that this combi- 

 nation takes place even at 0°. The other haptophorous group of the 

 intermediary body is possessed of less avidity and it is by means of 

 this that combination between the intermediary body and the com- 

 plement takes place ; and on account of the slight avidity of this 

 haptophorous group this combination occurs only at a relatively high 

 temperature. When an active serum is kept at 0° it contains the 

 intermediary body and the complement both in a free state ; now,^ if 

 susceptible erythrocytes be added to this serum still kept at 0°, the 

 corpuscles and the intermediary body combine, while the complement 

 remains free ; but when the temperature is raised to 37° the comple- 

 ment enters into the combination by attaching itself to the interme- 

 diary body. The haptophorous group by which the intermediary 

 body combines with the corpuscle is sometimes designated as hemo- 

 tropic. Of course, there may be in certain sera intermediary bodies 

 whose hemotropic groups have no greater avidity than their comple- 

 ment groups ; or there may be complements which combine with in- 

 termediary bodies at a low temperature. It may happen that the 

 intermediary body is contained in the serum of one animal while the 

 complement may be furnished by the blood of another animal. 

 This has been shown to be the case in the following experiment : 

 Dog serum dissolves the blood corpuscles of the guinea-pig with 

 great energy. If the dog serum be heated to 57° it loses its hemo- 

 lytic action on guinea-pig blood. But if inactive dog serum be 

 added to five c.c. of a five per cent, dilution of guinea-pig blood and 

 two c.c. of the serum of a normal guinea-pig be added to i^is mix- 

 ture, complete hemolysis occurs. This is explainable only on the 



'In his later papers Ehrlich has used the terms "immune hody" and "inter- 

 mediary body" interchangeably. 



