44 COLLECTED STUDIES IN IMMUNITY. 



serum and not to the activity of the phagocytes. That the taking 

 up of the blood-cells by the phagocytes in the specifically treated 

 guinea-pig is necessary for the solution of the blood-cells was ex- 

 cluded by the fact that haemolysis is also effected in the peritoneal 

 cavity of the animals apart from the phagocytic cells. Furthermore, 

 a transference by the phagocytes of the substances necessary for 

 solution was not suggested because the exudate, rich in leucocytes, 

 which was produced in specifically immunized guinea-pigs by in- 

 jections of an aleuronat mixture, showed a much smaller content 

 of both immune body and complement than the blood which was 

 poor in leucocytes. 



Metchnikoff has objected to these experiments. 1 He states that 

 aleuronat exudates contain principally microphages, whereas the 

 blood is richer in macrophages, and that the latter alone are con- 

 cerned in haemolysis. I have therefore tested the spleen (rich in 

 macrophages) of normal rabbits and guinea-pigs with a cattle blood 

 immune body derived from rabbits in order to determine the amount 

 of complement present. The experiments have demonstrated that 

 the spleen also contains much less complement than the blood serum. 

 For example, 1 grm. finely crushed spleen of an exsanguinated rabbit 

 was mixed with 4 cc. of an 8 p. m. NaCl solution. This fluid, like 

 similar mixtures derived from liver and kidney, when tested in the 

 usual manner proved from eight to sixteen times weaker than the 

 blood serum. Moreover, if the suspended organic particles were 

 first washed with physiological salt solution, they yielded no com- 

 plement whatever to the immune body. The spleen of a guinea-pig 

 contained still less complement, although the serum of this same 

 animal completely activated the cattle blood immune body derived 

 from rabbits, and did so in even smaller quantity than the rabbit 

 serum. 



We must therefore in conformity with the side-chain theory look 

 to the blood serum as the chief source of complement. 



It is self-evident that the complement cannot originate in the blood 

 plasma; it must, of course, be derived from some kind of cells. How- 

 ever, that it is especially abundant in the phagocytes is not at all 

 borne out by the above experiments. 



As for the immune body, Metchnikoff too believes this to circulate 

 free in the blood plasma. According to his conception the macro- 



1 Annales de PInst. Pasteur, 1899, No. 10. 



