Db. Murray on Vaccination. 347 



jower of Vaccine-Pox, in those vaccinated at a very early age, 

 and where the operation has been deferred till later in life, that 

 jio difference does exist, for this is no proof at all. 



From the references I have submitted, I think it can scarcely 

 J)e doubted that the constitutions of very young infants are 

 :Comparatively indisposed both to natural and inoculated Small- 

 Pox ; and the analogy between Small-Pox and Vaccine-Pox 

 is so strong, that there is every reason to suppose, that if the 

 former, which is a more virulent contagion, cannot easily be 

 .communicated in that stage of life, the latter will in all proba- 

 bility be even more difficultly communicated ; and there is 

 much reason to suspect, that if the constitutional susceptibilitv 

 be defective, although local disease may be produced by inocu- 

 lation with the virus, the general system will not become 

 influenced by it, in which case no protective power will be 

 imparted, however regular the local affection may be in its 

 course and appearance. 



Dr. Adams, in his work on Morbid Poisons, speaks very 

 .decidedly upon this point : — " That some constitutions, or even 

 some parts are insusceptible to a poison at one time, the 

 influence of which they feel at another, and also, that at certain 

 times the part to which a poison is applied is susceptible 

 thereof while the constitution will resist it; and that it is 

 therefore of the greatest consequence to attend to these states 

 of the constitution, as for want of such attention, many, no 

 doubt, have been lulled into a false security regarding their 

 protection against the variolous poison after vaccination." 



It is thus that superficial observation may be deceived where 

 local susceptibility alone exists ; and I have no doubt, from my 

 own child having taken the vaccine infection twice in the way 

 she did, that her constitution was insusceptible of its influence 

 the first time, although the course of the local disease was 

 normal. 



It appears to me that the Vaccine Virus is of so delicate a 

 nature that there are many unsuspected minor causes, which, 

 although they may not entirely prevent its assimilative process, 

 yet interfere so far as to modify its elaboration in the system, 

 and thus hasen its protective effect ; and my reason for thinking 

 so is, that we find such different degrees of protective power 

 manifested in different persons when brought to the test of 

 re-vaccination, or of exposure to variolous contagion. 



I myself have never seen Small-Pox after Vaccine-Pox, but 

 on making the experiment of re- vaccination, which I have done 

 in a number of cases at different jXJriods, from one month to 

 24 years after the primary operation, I have found the indivi- 

 duals endowed with very difl'erent degrees of protective power : 

 in the greater number there was insusceptibility of any local or 

 constitutional vaccine action : in two instances, both vaccinated 



