398 Chapter XII 



with that observed in the immunity against infective micro-organisms 

 is indeed very considerable. 



Having determined the part played by the macrophages in the 

 resistance of the organism of the animal against a not very soluble 

 salt of arsenic, Besredka proceeded to study the leucocytic phenomena 

 in poisoning by soluble arsenical compounds. In his experiments 

 he made use of potassium arsenite and he found that when lethal 

 doses were injected the guinea-pigs showed a diminution of leuco- 

 cytes in the blood in less than 24 hours, whilst with non-lethal doses, 

 he produced a marked hyperleucocytosis. When he injected lethal 

 doses into rabbits accustomed to arsenic, these animals manifested 

 an increase of white corpuscles, just as in animals injected with non- 

 lethal doses. These oscillations in the number of leucocytes, like 

 those which have been observed after poisoning by trisulphide of 

 arsenic, certainly indicate that the organism and its defensive cells 

 behave in the same way to both slightly soluble and very soluble salts 

 of arsenic. In the first case it was easy to demonstrate that the 

 accumulation of leucocytes in the blood and in the peritoneal exu- 

 dation terminated in the ingestion of the granules of trisulphide. 

 With potassium arsenite, it was not so easy to prove the point; a 

 chemical analysis of the elements of the blood, however, has given 

 a decisive answer. After injecting the lethal dose of this soluble 

 salt into rabbits accustomed to arsenic, Besredka bled them in order 

 to separate the plasma, leucocytes and red corpuscles. Several 

 experiments made on these rabbits gave a concordant result which 

 this observer sums up thus : " Although the bulk of plasma and of 

 red corpuscles was much greater than that of the leucocytes, it was 

 in the latter only that arsenic was found " by chemical analysis. It 

 was only in those cases where the animals survived, and manifested 

 hyperleucocytosis, that Besredka succeeded in demonstrating the 

 presence of arsenic in the white corpuscles. 



These experiments, excluding any doubt as to the protective part 

 played by the leucocytes against arsenical intoxication, of course 

 suggested the idea of investigating whether the nerve elements, sub- 

 mitted to the direct influence of potassium arsenite, exhibit any real 

 susceptibility to this poison. The injection of solutions of this salt 

 [419] into the brain demonstrated that the one-hundredth part of an ordi- 

 nary lethal subcutaneous dose was sufficient to cause fatal poisoning. 

 This fact, then, falls into line with other facts, already numerous, as 

 to the susceptibility of the nerve centres to microbial toxins, alkaloids 



