io8 NATURAL SCIENCE. Feb.. 



absolutely free from all matter derived from the body of the diseased 

 animal ; but with regard to all experiments on the subject, it is to be 

 wished it could be more conclusively shown that a more subtle 

 poison than the comparatively gross microbe may not be present. 

 It is assumed that the quantity of anything existing besides the 

 microbes in the original particles of injected matter would be so small 

 that after a few generations nothing could remain ; but in connection 

 with this we have to remember the extraordinary divisibility of 

 matter, and also that, conceivably, this other something may have 

 the power of increasing as well as the microbe. 



Might it not possibly be that the action of the oxygen^which 

 Pasteur thinks modifies the microbe — gradually destroys this other 

 poison ? and might not the phenomena of protective inoculation 

 be an acclimatisation of the system to gradually increasing doses of 

 poison, akin to that by which a man can accustom himself to larger 

 and larger doses of arsenic and opium ? But this is the merest 

 suggestion. 



It involves, moreover, the larger question of whether the experi- 

 ments of Pasteur and others really necessitate the belief that the 

 microbe is the sole and primary cause of the disease, and cannot be 

 treated of here. 



The above remarks apply to attenuated viruses in which the 

 microbe itself is supposed to be the active agent. But many recent 

 investigators, instead of using an attenuated culture of the microbe 

 for inoculation, inject small quantities of the toxic principle produced 

 by its growth. After the culture has proceeded to a certain extent, 

 it is carefully sterilised, and the toxic principle is obtained free from 

 microbes or their germs. To such methods of inoculation the 

 exhaustion theory, of course, does not apply. 



It has even been shown, in the case of the bacillus of tetanus, 

 that it is the toxic principle, and not the microbe, which causes the 

 disease. Thus MM. Vaillard and Vincent7 assert that if the inocu- 

 lation be effected with a culture in which the bacillus has not had 

 time to produce the toxic principle, or with a culture further advanced, 

 but washed, so as to get rid of the poison, the symptoms of tetanus 

 are not produced. On the other hand, a very small dose of the toxic 

 principle does produce them. 



MM. Rodet and Courmont,^ 'tgain, have shown that in the 

 cultures of Staphylocoque pyozhie there are two distinct principles, 

 which can be separated by the action of alcohol. The one, insoluble 

 in alcohol, has a prophylactic value ; the other, soluble in alcohol, 

 renders an animal more susceptible to the disease produced by the 

 microbe. Thus, while animals inoculated with the former are more 

 or less protected from the disease, those inoculated with the latter 

 are rendered more susceptible to it. 



Coinptes Renins, vol. cxii., p. 239. " Comptes Rcmlus, vol. cxiii., p. 432. 



