190 Chapter VII 



organisms remain alive in the plasmas of the exudations and are, in 

 this condition, ingested by the phagocytes, it was therefore very im- 

 portant that this fundamental contradiction should be settled by 

 decisive experiments. The attempt has often been made to obtain 

 blood plasma and to compare its bactericidal action with that of 

 serum from the same animal. In the preceding chapter we have already 

 mentioned an attempt in this direction made by Sawtchenko. Hahn^ 

 had previously attempted to prepare plasma by adding histon to blood. 

 As this " plasma " was found to be just as bactericidal as the blood 

 serum Hahn concluded that the bactericidal substance, secreted by 

 the living leucocytes, circulates in the living blood. In all the experi- 

 ments carried out by this method it was impossible to avoid certain 

 sources of error, and in my laboratory Gengou^ undertook a new 

 series of researches, endeavouring to obtain from blood a fluid re- 

 sembling normal plasma as closely as possible. The method he 

 employed has been described in detail in a memoir, on an anti- 

 coagulating serum, which he published along with Bordet^ The 

 blood was drawn into paraffined tubes and centrifugal ised at once 

 in other tubes whose walls were likewise covered with a layer of 

 [201] paraffin. The fluid thus prepared is certainly more allied to circu- 

 lating plasma than is the blood serum obtained after the coagulation 

 of the blood. Nevertheless, it is still far from being identical with 

 true normal plasma ; it still coagulates, though tardily. Gengou 

 compared, in their bactericidal action, the blood serum and the serum, 

 decanted after the tardy coagulation of the fluid analogous to 

 plasma. He carried out a great number of experiments Avith the 

 two fluids, obtained from dogs, rabbits and rats, making a comparative 

 study of their bactericidal power as regards the anthrax bacillus, the 

 typhoid bacillus, and the cholera vibrio. I have closely followed all 

 these experiments and can confirm the results described by Gengou, 

 namely, that the fluid, in this plasma serum, possesses an insignificant 

 bactericidal power or none at all, whilst the blood serum almost 

 always exhibits this property to a marked degree. 



As a result of the researches just summarised it is no longer 

 possible to maintain the theory of bactericidal secretions by leuco- 

 cytes or by any other category of cells. The bactericidal substance 



1 Arch.f. Hyg., Munchen u. Leipzig, 1895, Bd. xxv, S. 105; Berl. klin. Wchiischr., 

 1896, S. 864. 



' Ann. de VInst. Pasteur, Paris, 1901, t. xv, p. 232. 

 3 lUd., p. 129. 



