®R. MuRHAY Oil Vaccination. 3-19 



So many circunistaiiccs interfere w<lh the perfect action of 

 -\acciiui ill the coiislitution, and so important and essential is its 

 perfection for the safety of individuals and the community, that 

 every precaution sliould be taken to have it observed in the most 

 satisfactorj manner; and Mr. Boyce's ingenious and invaluable 

 test of a double inoculation on the fifth day, ought not to be 

 neglected, as it affords a true and positive criterion, whether or 

 siot the virus has infected the constitution w-hen the fever is 

 inconsiderable. 



The great point, Jiowevcr, which every one wislics to know, 

 is — -whether the most perfect impregnation of the system with 

 the vaccine disease affords a complete security against variolous 

 infection ? and this I can only answer as a Military practitioner, 

 and as such I can say, that from the universal adoption of 

 \aceination in the army, and from the careful manner we are 

 obliged to obseive, note, and report annually upon its effects in 

 every case, Small-Pox has become a very rare disease in our 

 sick returns, whilst the exposure of soldiers to variolous con- 

 tagion is so frequent and unavoidable, tliat I think the fabric of 

 vaccination must have been shaken by our experience, if its 

 foundation had not been secure. Dr. tfennen, one of our best 

 Military writers, observes, — " The Small-Pox has raged around 

 our Camps and Barracks, and carried off its victims from under 

 our very walls, and even from the houses where our detached 

 Troops liave been quartered, while it has left them unmolested." 



It is, howevei', in the nature of all morbid phenomena, to be 

 liable to objection, and it ought to be borne in mind, that as the 

 most constant and characteristic law of Small-Pox itself, viz. 

 that of its only affecting a person once in life, is frequently 

 violated, so it is tlierefore quite conformable to analogy, and 

 may be expected, that the most jterfect Vaccine-Pox will not in 

 all cases prove a complete security against Small-Pox, nor 

 against re-infection with its own virus ; for tlicrc are some con- 

 btitulions in wliich susceptibility seems to persist, and to 

 overcome the ordinary protecting influence of both vaccine and 

 variolous inoculation. In such constitutions, regular Small-Pox 

 and \arioloid eruptions, accompanied with fever, have been 

 known to occur for a second and even for a third time after 

 both regular Small-Pox and Vaccine-Pox. 



It is, no doubt, however, from the careless way in which vac- 

 -cination has often been conducted, and from the opinion first 

 entertained, that its anti-variolous power was absolute in wliich- 

 evcr way it was performed, so it was performed at all, that its 

 efficacy is now undervalued by some persons far below its real 

 deserts, and that a check has been given to the practice of 

 vaccination in some parts ; but, admitting tliat it is not invari- 

 ably a secure defence against the inroads of Small-Pox ; and 

 that differences of opinion exist upon some particular points 



