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SUMMARY OF CURRENT RESEARCHES RELATING TO 
marked. He was of opinion that it was quite possible to accept both 
views of the question. The controversy had taken place chiefly as to 
the phenomena observed in the rat ; in that animal phagocytosis was 
only to be observed with difficulty, and the serum of rat’s blood un- 
doubtedly possessed bacteria-killing properties to a high degree. 
l)r. Klein stated that frogs and rats were insusceptible to anthrax, 
but that these animals could be made susceptible to the disease by a 
variety of means, indicating that their normal power of resistance 
was due to certain chemical conditions of the blood. If the bacillus 
of anthrax was introduced into the lymph-sac of a chloroformed frog, 
this animal always died of anthrax. Rats inoculated with anthrax and 
kept under the influence of an anaesthetic also died of anthrax. He had 
been unable to find any evidence to show that in these cases the leuco- 
cytes had lost their power of swallowing up bacteria, and therefore the 
susceptibility of chloroformed animals to anthrax could only be ex- 
plained by some chemical changes taking place in the serum of the 
chloroformed rat or frog. 
Dr. Metschnikoff said that, of all the objections which have been raised 
against the theory of phagocytes, doubtless by far the most important 
was that formulated by Behring aud Nissen : namely, the fact that the 
serum of guinea-pigs vaccinated against the vibrio of Metschnikoff had 
bactericidal powers on the same vibrio. Whilst the serum of normal 
guinea-pigs allowed the free development of a large number of these 
microbes, the serum of vaccinated animals killed the micro-organisms at 
the end of a few hours. MM. Behring and Nissen were convinced that 
this fact formed a complete explanation of the acquired immunity of 
guinea-pigs against the Vibrio Metclmikoji , and that it might serve as a 
model for a theory of immunity. His own researches, however, proved 
the contrary. If one studied the phenomena as they occurred in the 
living animal, one noticed at once that the bacilli inoculated into 
immune guinea-pigs remained alive for a very long time. Some vibrios 
were taken into the interior of leucocytes at the point of inoculation, 
whilst others developed perfectly in the liquid exudation. To show 
this, one had only to take a drop of the latter, and place it in the warm 
chamber ; the leucocytes perished when taken out of the organism, and 
allowed the bacilli contained in their interior to develope freely. The 
vibrios thus multiplied and filled the leucocytes, which swelled and 
eventually burst, allowing the microbes to pass freely into the liquid 
part of the exudation. Here the development continued, and one ob- 
tained very abundant cultures from the liquid exudation of the immune 
guinea-pig. If one extracted a small quantity of such a culture, and in- 
troduced it into the dead serum of an immune guinea-pig, this serum 
not only did not kill the bacilli, but also gave a more abundant develop- 
ment than the serum of a non-immune animal could do. The study of 
the phenomena in living animals made artificially immune against the 
vibrio of Metschnikoff, instead of overthrowing the theory of phago- 
cytosis, furnished on the contrary an evident proof in its favour. The 
theories of the attenuation of virus in the bodies of immune animals, and 
of the neutralization of the toxines, could not be applied to his case, as 
the vibrios remained very virulent, and because the immune guinea-pigs 
are as sensitive to the toxine of the bacillus as the non-immune animal. 
