VACCINATION AGAINST SMALLPOX 197 



sensibly, does not arise primarily front the first action of 

 the virus on the constitution, but that it often comes on, if 

 the pustule is left to chance, as a secondary disease. This 

 leads me to conjecture, what experiment must finally deter- 

 mine, that they who have had the smallpox are not after- 

 wards susceptible of the primary action of the cow-pox 

 virus; for seeing that the simple virus itself, when it has 

 not passed beyond the boundary of a vesicle, excites in the 

 system so little commotion, is it not probable the trifling 

 illness thus induced may be lost in that which so quickly, 

 and oftentimes so severely, follows in the casual cow-pox 

 from the presence of corroding ulcers? This considera- 

 tion induces me to suppose that I may have been mistaken 

 in my former observation on this subject. 



In this respect, as well as many others, a parallel may be 

 drawn between this disease and the smallpox. In the latter, 

 the patient first feels the effect of what is called the ab- 

 sorption of the virus. The symptoms then often nearly re- 

 tire, when a fresh attack commences, different from the 

 first, and the illness keeps pace with the progress of the 

 pustules through their different stages of maturation, ulcera- 

 tion, etc. 



Although the application I have mentioned in the case of 

 Mary Hearn proved sufficient to check the progress of 

 ulceration and prevent any secondary symptoms, yet, after 

 the pustule has duly exerted its influence, I should prefer 

 the destroying it quickly and effectually to any other mode. 

 The term caustic to a tender ear (and I conceive none feel 

 more interested in this inquiry than the anxious guardians 

 of a nursery) may sound harsh and unpleasing, but every 

 solicitude that may arise on this account will no longer 

 exist when it is understood that the pustule, in a state fit 

 to be acted upon, is then quite superficial, and that it does 

 not occupy the space of a silver penny." 



As a proof of the efficacy of this practice, even before 

 the virus has fully exerted itself on the system, I shall lay 

 before my reader the following history: 



* I mention escharotics for stopping the progress of the pustule because 

 I am acquainted with their efficacy; probably more simple means might 

 answer the purpose quite as well, such as might be found among the mineral 

 and vegetable astringents. 



