Facts hearing on acquired immunity 209 



products of the septic vibrio and of the bacillus of symptomatic 

 anthrax. And now, as the result of these investigations, vaccinations 

 by microbial products are in everyday use in all research laboratories. 

 The vaccinations now used (anthrax, symptomatic anthrax, swine 

 erysipelas and rabies) are still being carried out by means of the 

 inoculation of living viruses. 



The comparative history of acquired immunity is still very in- 

 complete. The facts known concerning the adaptation of unicellular 

 organisms to all kinds of injurious influences of a physical or chemical 

 nature enable us to perceive that acquired immunity is just as general 

 in living beings as is natural immunity ; but it is impossible, in the 

 present state of our knowledge, to confirm this hypothesis by exact 

 and experimental data. The reason for this lies in the great difficulty 

 we have in carrying out experiments on the lower animals. The 

 majority of the Invertebrata in captivity do not remain alive long 

 enough and can not be sufficiently often inoculated for us to obtain 

 in them a well marked acquired immunity against micro-organisms. 

 Kowalevsky^, the celebrated Russian zoologist, has tried to overcome 

 these various difficulties by making use of Myriapods. He found first 

 that Scolopendrae, when inoculated with anthrax bacilli, die there- 

 from during the heats of summer, the blood containing a number 

 of anthrax bacilli. But when the temperature does not exceed 1 7° — 

 18° C, a fairly large number of these myriapods survive. The same 

 survival was observed when Pasteur's first vaccine was injected. Kow- 

 alevsky utilised the Scolopendrae that had resisted the first injection 

 of anthrax bacilli to ascertain whether they had contracted an acquired 

 immunity. The results were not absolutely demonstrative and Kow- 

 alevsky sums up his results in the following words : " I cannot say, 

 therefore, that I have succeeded in solving this question of vaccina- 

 tion, but it appears to me very probable " (p. 607). 



In view of this doubt, I asked Mesnil to make a fresh attempt, 

 making use of Scolopendrae and inoculating them with anthrax 

 bacilli. These creatures, however, were so delicate and so little 

 capable of remaining alive under the artificial conditions of their 

 captivity, that the attempt soon had to be abandoned. I tried to 

 obtain better results with the larvae of Oryctes naslcornis; here [221] 

 again the difficulties were too great. These insects exhibit a 

 perfect natural immunity against certain micro-organisms, but for 

 others they showed an insurmountable susceptibility. It is very 

 ^ Arch, de zool. exper.y Paris, 1895, 3' serie, t iii, p. 591. 

 B. 14 



