Mechanism of immunity against micro-organisms 189 



rabbits' leucocytes with the serum of a different species heated to 

 60 C., Laschtschenko believes himself safe from the objection that the 

 giving up of the bactericidal substance results from the death or 

 injury of the white corpuscles. According to him this injurious 

 effect on the white corpuscles can only be produced by an unstable 

 substance which is destroyed by heating to 60 C. Laschtschenko 

 forgets that the leucocytes are in general delicate cells, capable of 

 being affected even by fluids which do not actually kill them. Xow 

 we know that serums, when heated to 60 C., still retain their power 

 of agglutinating the leucocytes, a power which must hamper these 

 cells in their normal function. 



Trommsdorff 1 , in an investigation carried out in Buchner's labo- 

 ratory, endeavoured to supplement Laschtschenko's results and to 

 support them by new and more convincing experiments. But he 

 only succeeded in a few cases in obtaining a bactericidal serum after 

 adding rabbits' leucocytes to the blood serum of other animals. 

 "In a great number of my experiments," says Trommsdorff, "I 

 very often did not succeed in extracting the alexines from the 

 rabbit's leucocytes by the use of Laschtschenko's method " (p. 385). 

 On the other hand, Trommsdorff, wishing to establish the living 

 condition of the leucocytes mixed with a foreign serum, arrived at 

 the following result: "In the majority of the cases, as in fresh 

 exudations, the number of living leucocytes after their treat- [200] 

 ment with active horse's serum, as well as with inactive serum 

 (heated to 60 C.) of dog, ox and horse, varied between 60 and 

 80 /o" (p. 391). In spite of these verifications, Trommsdorff comes 

 to the conclusion that the presence of alexine in those serums to 

 which leucocytes had been added, must "in all probability" be 

 attributed to its secretion by the living leucocytes. We regard it 

 as much more probable that the alexine, in those cases where it 

 passed into the serum, was due to the breaking up of the dead 

 leucocytes, whose numbers rose to 40 /o, that is to say, almost 

 half their total number. Our conclusion is, in any case, much 

 more in accord with the more constant and more exact results 

 obtained by other methods. 



In spite of the insufficiency of proofs in favour of the theory of 



bactericidal secretions by the leucocytes it has been very favourably 



received by many investigators. As, however, it came into collision 



with the general fact that, in the refractory animal, the micro- 



1 Arch.f. Hyg., Munchen u. Leipzig, 1901, Bd. XL, S. 382. 



