426 BLOOD AND LYMPH. 



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 the solution of the corpuscles 

 depends upon the combined action of two substances. This 

 point has been made clear particularly in regard to the snake- 

 poisons, such as cobra venom. In these venoms there is present 

 a substance analogous to the immune body or amboceptor, but 

 in order for it to affect the red corpuscles it must be activated 

 by a complement of some sort, present in the plasma or the red 

 corpuscle itself. Kyesf has given some interesting facts to 

 prove that lecithin is an effective complement for these venoms, 

 and that probably it is this definite substance which is furnished 

 by the blood in activating the venom toxin. 



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 differencss are shown in this respect. 

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



* Bordet, "Studies in Immunity," translated by Gay, New York, 1909. 

 t Kyes, "Berl. klin. Wochenschrift," 1902 and "1903. 



