274 



On Vaccination. 



[April, 



the complication of a scurvy eruption of a bad character joined 

 with a predisposition to a typhous fever. Thus none of the 

 deaths can be ascribed to the nature or character of the cow-pox 

 itself : aU are the consequence of other diseases well known^ or 

 produced by accidents ; the causes of which, independent of 

 vaccination, but coincident with it, may be completely appre- 

 ciated by what we have said above. 



FOURTH aUESTION. 



Is the virus introduced hy vaccination of suck a nature as t» 

 produce, even after its operation is happily finished, diseases^ 

 more or less severe, and which may even prove fatal P 



The solution of this question is difficult, because our investi- 

 gation is of necessity interrupted by a great number of uncer- 

 tainties. 



If is certainly difficult to establish, that a virus, introduced 

 into the body, and capable of rendering it inaccessible to the 

 smali-pox contagion, has not the power of producing any other 

 change which can affect the health. Sucli a consequence can 

 only be the result of a number of observations, so great that its 

 disproportion with the contrary observations prevents us from 

 ascribing them to any thing else but causes absolutely uncon- 

 nected with the introduction of the virus. 



But the observations in support of a contrary opinion must 

 be equally difficult to obtain. If a disease appears after vacci- 

 .nation, in order to show that it can be ascribed to no other 

 cause, we ought to know what was the state of the subject before 

 vaccination, and whether his constitutional or hereditary dispo- 

 sitions did not prepare him for those maladies which have taken 

 place. We must be able to show th^t after vaccination he has 

 not been exposed to causes capable of producing these diseases. 

 We ought likewise to inquire whether the source from which 

 the cow-pox matter v/as derived was infected with any foreign 

 ferment. And finally, as in all ages and ail circumstances of 

 life various diseases appear which cannot be assigned to any 

 known cause, those which succeed vaccination ought, in order 

 to be ascribed to it, to shov/ such a character of affinity with 

 each other as to indicate their common origin^ and' offer in their 

 developement^ .connection more or less sensible with the primi- 

 tive eifects of vaccination to which they succeed. 



It is therefore requisite to admit, in opposition to the advan- 

 tages ascribed to vaccination, those observations only which are 

 v/ell authenticated, and the details of which are sufficiently 

 complete to enable us to appreciate their value. 



Nevertheless, if the number of facts alleged were very consi- 

 derable^ as it would be impossible ia such a case to ascribe them 



