September 25, 1896.] 



SCIENCE. 



421 



rious other conditions are necessary to the 

 production of an attack of cholera besides 

 the mere presence of the vibrio, yet it is the 

 essential materies morbi ; and it is by the aid 

 of the diagnosis which its presence in any 

 case of true cholera enables the bacteriolo- 

 gist to make, that threatened invasions of 

 this awful disease have of late years been 

 so successfully repelled from our shores. If 

 . bacteriology had done nothing more for us 

 than this it might well have earned our 

 gratitude. 



I have next to invite your attention 

 to some earlier work of Pasteur. There 

 is a disease known in France under 

 the name of cholera des pontes, which 

 often produced great havoc among 

 the poultry yards of Paris. It had been 

 observed that the blood of birds that 

 had died of this disease was peopled 

 by a multitude of minute bacteria, not very 

 dissimilar in form and size to the mi- 

 crobe of the lactic ferment to which I have 

 before referred. And Pasteur found that, 

 if this bacterium was cultivated outside the 

 body for a protracted period under certain 

 conditions, it underwent a remarkable di- 

 minution of its virulence ; so that, if in- 

 oculated into a healthy fowl, it no longer 

 caused the death of the bird, as it would 

 have done in its original condition, but pro- 

 duced a milder form of the disease which 

 was not fatal. And this altered character 

 of the microbe, caused by certain conditions, 

 was found to persist in successive genera- 

 tions cultivated in the ordinary way. Thus 

 was discovered the great fact, of what 

 Pasteur termed attenuation des virus, which 

 at once gave the clue to understanding 

 what had before been quite mysterious, the 

 difference in virulence of the same disease 

 in different epidemics. 



But he made the further very important 

 observation that a bird which had gone 

 through the mild form of the complaint had 

 acquired immunity against it in its most 



virulent condition. Pasteur afterwards 

 succeeded in obtaining mitigated varieties 

 of microbes for some other diseases ; and 

 he applied with great success the principle 

 which he had discovered in fowl- cholera 

 for protecting the larger domestic animals 

 against the plague of anthrax. The prepa- 

 rations used for such preventive inocula- 

 tions he termed ' vaccins' in honor of our 

 great countryman, Edward Jenner. For 

 Pasteur at once saw the analogy between 

 the immunity to fowl-cholera produced by 

 its attenuated virus and the protection af- 

 forded against small-pox by vaccination. 

 And while pathologists still hesitated, he 

 had no doubt of the correctness of Jenner's 

 expression variolce vaccince, or small-pox in 

 the cow. 



It is just a hundred years since Jenner 

 made the crucial experiment of inoculating 

 with small-pox a boy whom he had pre- 

 viously vaccinated, the result being, as he 

 anticipated, that the boy was quite unaf- 

 fected. It may be remarked that this was 

 a perfectly legitimate experiment, involving 

 no danger to the subject of it. Inoculation 

 was at that time the established practice ; 

 and if vaccination should prove nugatory, 

 the inoculation would be only what would 

 have been otherwise called for ; while it 

 would be perfectly harmless if the hoped-for 

 effect of vaccination had been produced. 



We are a practical people, not much ad- 

 dicted to personal commemorations ; al- 

 though our nation did indeed celebrate,with 

 fitting splendor, the jubilee of the reign of 

 our beloved Queen ; and, at the invitation 

 of Glasgow, the scientific world has lately 

 marked, in a manner, though different, as 

 imposing, the jubilee of the life-work of a 

 sovereign in science (Lord Kelvin). But 

 while we cannot be astonished that the cen- 

 tenary of Jenner's immortal discovery 

 should have failed to receive general recog- 

 nition in this country, it is melancholy to 

 think that this year should, in his native 



