400 BLOOD AND LYMPH. 



by Bordet, Ehrlich, and others.* It has been shown that they 

 are in reality composed of two substances whose combined action 

 is necessary for the hemolysis. There is, first, a new and specific 

 substance that is produced by the body as a consequence of the 

 injection of the foreign blood corpuscles. This substance has been 

 given different names, but is known most frequently (Ehrlich) 

 as the immune body (or amboceptor). It is not destroyed by mod- 

 erate heating. The immune body is enabled to act upon the 

 corpuscles by the co-operation of certain substances which are 

 normally present in the serum and are therefore not produced by 

 the process of immunization. These substances are known usually 

 as complements, and it is they that are destroyed by heating to 

 55 C. If the immune serum of a guinea pig is heated to 55 C. 

 its hemolytic action upon rabbits' corpuscles is destroyed. The 

 action may be restored, however, by adding a little of the rabbit's 

 own serum, since in terms of the above hypothesis the complements 

 are present in normal serum. That is to say, an experiment of 

 the following kind may be performed. Washed blood corpuscles 

 of a rabbit plus immune serum from a guinea pig show hemolysis. 

 Washed blood corpuscles of a rabbit plus immune serum which has 

 been made inactive by heating show no hemolysis. Addition of 

 normal rabbits' serum to this latter mixture again activates the 

 immune serum and causes hemolysis. The rabbits' serum in this 

 case supplies the needed complement. 



These facts, it should be stated, are interpreted somewhat differently 

 by Bordet. The immune substance he designates as a "substance sensibila- 

 trice" and the complement as alexin. The latter forms the protective sub- 

 tance of the blood, but is unable to act upon the foreign cells until these 

 latter have been changed in some way, that is, sensitized by the specific 

 immune substance developed during the process of immunizing. 



In the case of some of the natural hemolysins referred to above 

 it has also been shown that they are composed in reality of two 

 bodies, each necessary to the reaction, one the complement, de- 

 stroyed by heating, and one comparable to the immune body, 

 but in this case designated as the interbod}/ or intermediary body, 

 since it is not produced by immunization. 



Speaking in general terms, the serum of any animal is more or 

 less hemolytic in relation to the blood corpuscles of an animal of 

 another species; but great differences are shown in this respect. The 

 blood-serum of the horse shows but little hemolytic action upon the 

 red corpuscles of the 'rabbit when compared with the effect of the 

 serum of the dog or cat. Eels' serum has a remarkably strong 



* For a brief statement of the development of the subject, see Wasser- 

 mann, "Immune Sera, Hemolysins, Cytotoxins, and Precipitins, " trans- 

 lated by Bolduan, New York, 1904. For a more extended review, see Aschoff, 

 "Zeitschirft f. alhremeine Physiologic," 1, 69, 1902, or Ehrlich, " Collected 

 Studies on Immunity/' translated by Bolduan, New York, 1906. 



