Artificial immunity against toxins 401 



cases, there is clearly a development of antibodies, such as the 

 fixatives, whose phagocytic origin may reasonably be claimed, but 

 no true antitoxins. It must not be forgotten, however, that the 

 various kinds of phagocytes present, amongst themselves, great 

 differences, and that perhaps certain only of these elements are 

 capable of producing antitoxins. When micro-organisms, living or 

 dead, are introduced into an animal it is found that antitoxins do 

 not as a rule appear in the fluids; in these cases the reaction is 

 set up mainly by the microphages. The macrophages represent 

 the principal source of antitoxins. In cases where these phagocytes 

 ingest the micro-organism the blood exhibits an undoubted antitoxic 

 power. Such is the case with bubonic plague in the human subject, 

 where the micro-organism is readily ingested by the macrophages. 

 Here we obtain antitoxic serums even after the introduction of living 

 or dead organisms into the animal, a fact observed by Roux and 

 his collaborators. Another fact in favour of the hypothesis I am 

 defending is furnished to us by the cayman. As noted above, this 

 reptile, of all known animals, supplies antitoxins most quickly and 

 easily. In the cayman the leucocytic system is composed of eosino- 

 phile microphages filled with granules, and of macrophages. As the 

 eosinophile cells are only very weakly phagocytic, it is the macro- 

 phages almost exclusively which intervene in the reaction against 

 the micro-organisms. It is probable, then, that in the cayman and 

 in animals inoculated with the plague bacillus the exclusion of the 

 microphages from the struggle constitutes a factor favourable to the 

 production of antitoxins and at the same time favourable to the 

 manifestation of the activity of the macrophages. 



If these latter phagocytes play the primary role in the excretion 

 of antitoxins in the fluids of the body we should expect to find this [422] 

 function exercised not only by the motile macrophages of the blood 

 and lymph, but also by the fixed macrophages, so widely diffused 

 through almost all the organs. 



I advance this hypothesis for what it is worth, simply as a guiding 

 idea for new researches in this field, of which so much is still un- 

 known 1 . The brief account of the actual state of the question of 



1 Homer's recent researches (Arch. f. Ophth., Leipzig, 1901, Bd. LIT, S. 72) on 

 anti-abrin accord very well with our hypothesis. He was able to demonstrate that 

 the spleen, the bone-marrow, and the conjunctiva of the eye, when submitted to the 

 influence of abrin, contain a notable quantity of anti-abrin. Now these three organs 

 are very rich in phagocytes. 



B. 26 



