Sect. XXXIII. 2. 10. OF SENSATION. 315 



into any diforder. At the fame time both the meafles and fmall- 

 pox feem to have been rendered milder. Does not this give an 

 idea, that if they were both inoculated at the fame time, that 

 neither of them might affect the patient ? 



From thefe cafes I contend, that the contagious matter of 

 thefe difeafes does not affect the conftituiion by a fermentation, 

 or chemical change of the blood, becaufe then they muft have 

 proceeded together, and have produced a third fomething, not 

 exactly fimilar to either of them : but that they produce new 

 motions of the cutaneous terminations of the blood- veffels, 

 which for a time proceed daily with increafmg activity, like 

 fome paroxyfms of fever, till they at length fecrete or form a 

 fimilar poifon by thefe unnatural actions. 



Now as in the meafles one kind of unnatural motion takes 

 place, and in the fmall-pox another kind, it is eafy to conceive, 

 that thefe different kinds of morbid motions cannot exift togeth- 

 er •, and therefore, that that which has firft begun will continue 

 till the fyftem becomes habituated to the ftimulus which occa- 

 fions it, and has ceafed to be thrown into action by it ; and then 

 the other kind of ftimulus will in its turn produce fever, and 

 new kinds of motions peculiar to itfelf. 



10. On further considering the action of contagious matter, 

 fince the former part of this work was fent to the prefs ; where 

 I have afferted, in Sect. XXII. 4. 3. that it is probable, that the 

 variolous matter is diffufed through the blood ; I prevailed on 

 my friend Mr. Power, furgeon at Bofworth, in Leicefterlhire, to 

 try, whether the fmall-pox could be inoculated by ufing the blood 

 of a variolous patient inftead of the matter from the puftules ; 

 as I thought fuch an experiment might throw fome light at 

 ieait on this interefting fubject. The following is an extract 

 from his letter : — 



"March 11, 1793. I inoculated two children, who had not 

 had the fmall-pox, with blood ; which was taken from a patient 

 on the fecond day after the eruption commenced, and before it 

 was completed. And at the fame time I inoculated myfelf with 

 blood from the fame perfon, in order to compare the appearances, 

 which might arife in a perfon liable to receive the infection, arid 

 in one not liable to receive it. On the fame day I inoculated 

 four other children liable to receive the infection with blood 

 taken from another perfon on the fourth day after the com- 

 mencement of the eruption. The patients from whom the blood 

 was taken had the diieafe mildly, but had the molt puftules of 

 any I could felect from twenty inoculated patients ; and as 

 much of the blood was infinuated under the cuticle, as I could 

 introduce by elevating the f&in without drawing blood j and 



three 



