II Artificial immunity against toxins 399 



fXidi other poisons. But in the case of potassium arsenite, it was 

 iieven more easily demonstrated than in the other cases that immunity 

 natural or acquired, is connected with the absorption of the poison 

 by the leucocytes. These cells, themselves much less susceptible to 

 the toxic action than are the nerve elements, protect them from 

 contact with the poison. 



It is manifest that arsenic is not the only mineral substance 

 capable of being absorbed by the phagocytes, and there are already 

 on record well established facts in support of this thesis. Some time 

 previous to the researches on arsenical poisoning just summarised, 

 Kobert, then in Dorpat, set his pupils, Stender, Samo'iloff, Lipsky 

 and others^ to make systematic researches on the fate of iron in 

 the animal organism. For this purpose these observers made use 

 of a very soluble preparation of iron — or better expressed, as 

 soluble as possible — Dr Hornemann'syerrifm oxy datum saccharatum 

 soliibile, which does not precipitate in alkaline media. They proved 

 that a . small quantity of the iron introduced into the animal is 

 eliminated by the kidneys and the wall of the intestine, but that 

 the greater part of the metal is arrested in the organs, especially 

 the liver, spleen and bone marrow. The iron is there absorbed 

 by the leucocytes which hold it for some time and then throw it 

 into the intestine. 



I have had the opportunity of observing this circulation of 

 Dr Hornemann's soluble salt in the organism of several species of 

 vertebrates. Some time after its introduction into the organism by 

 the blood vessels, peritoneally or subcutaneously, the iron may be 

 found (by means of the microchemical reaction with potassium 

 ferrocyanide) accumulated in the various phagocytes, especially the 

 leucocytes, the stellate Kupffer's cells of the liver and the macro- 

 phages of the splenic pulp. The non-phagocytic cells, as, for example, 

 Ehrlich's basophile leucocytes, so abundant in the lymph of rats, 

 take up very little of this iron, although the macrophages and micro- 

 phages are full of \i\ Against these facts Weigert^ has advanced [420] 

 the objection that the leucocytes absorb only the iron precipitated 

 in the form of granules, but my own researches allow of no doubt 

 that not only granular but dissolved iron is absorbed. This dis- 



1 Arb. d. pharmak. histit. z. Dorpat, 1893, 1894, Bde vii— X. 



2 Ann. de VInst. Pasteur, Paris, 1894, t. viii, p. 719. 



3 Lubarsch u. Ostertag's Ergehnisse d. allg. Path., Jahrg. iv for 1897, 

 Wiesbaden, 1899, S. 107. 



