INVEETEBBATA, CRYPTOGAMIA, MICROSCOPY, ETC. 1011 



manner beings which need gas, and are always ready to seize upon 

 the oxygen. 



But is this the only possible explanation of the phenomena ? Not 

 strictly speaking. We can account for the facts of non-recurrence if 

 we assume that instead of removing and destroying certain substances 

 in the body of the animals, the life of the microbion introduces certain 

 others which are a hindrance to tho further development of this 

 microbion. The life-history of the lower organisms, and in general 

 of all organisms, justifies such an assumption. The excreta produced 

 by the vital processes may oppose a vital function of the same species. 

 In certain fermentations antiseptic products are seen to arise, during 

 and as the result of the fermentation, which put an end to the active 

 life of the ferments and to the fermentation long even before this. 

 A formation might take place during the cultivation of our microbion 

 of products whose presence would strictly explain the immunity and 

 the vaccination. 



But our artificial cultivation of the parasite allows us to control 

 this hypothesis as well. Let us prepare an artificial growth of the 

 microbion, and after evaporating it under the influence of cold and in 

 a vacuum, restore it to its original volume by a cultivating solution. 

 If the extract contains what is a poison to the life of the micro- 

 bion, and if this is a reason for cultivation being impossible in the 

 filtered liquid, then the sowing in the fresh medium should prove 

 unfruitful ; but it is not so. Thus it is impossible to believe that 

 substances appear during the life of the parasite which are able to 

 oppose its further development. This observation confirms, on the 

 contrary, the former theory, given above, with regard to the causes of 

 the non-recurrence of certain infectious diseases." 



A further fact in support of his views of the nature of tho 

 immunity and the vaccination was communicated by M. Pasteur to the 

 Academy : * In well-vaccinated and healthy fowls sometimes appear, 

 in one part or other of the body, boils, full of pus, which have caused 

 no injury to tho health of the bird. It was remarkable that these 

 boils originated from the cholera microbion which was preserved in 

 them as in a closed vessel, and doubtless was only imablc to rejiroduce 

 itself because the fowl was vaccinated. The pus could be taken from 

 the boils and cultivated, or fresh fowls could be inoculated with it, 

 in which it developed largely and killed them in tho ordinary 

 way. These facts remind us of the observations which M. Pasteur 

 described in his first memoir on the bcliaviour of tho guinea-pig with 

 regard to inoculation with tho poison of fuwl-cholera. 



]\r. Pasteur lias followed up f his experiments in fowl-cholera by in- 

 vestigating with regard to the germ-theory the case of a patient aftlicted 

 with an intermittent eruption of boils. He found the matter formed 

 in the cones of the boils to produce, when added to a proper culti- 

 vating liquid, numerous microscopic spherical bodies united together, 

 generally in pairs. The same occurred with matter taken from a loss 

 advanced boil. Diflfercntial experiments showed tho production of 



• 'Comptca Kcndus,' xc. (18S0) pp. 1030-3. Cf. ' Nuturforschcr,' xiii. (1880) 

 p. 218. t Il>id-, PP- 1033-44. 



