VACCINATION AGAINST SMALLPOX 201 



times it will even produce an ichorous fluid, and yet the 

 system will not be affected. The same thing we know hap- 

 pens with the smallpox virus. 



Four or five servants were inoculated at a farm contiguous 

 to this place, last summer, with matter just taken from an 

 infected cow. A little inflammation appeared on all their 

 arms, but died away without producing a pustule; yet all 

 these servants caught the disease within a month after- 

 wards from milking the infected cows, and some of them 

 had it severely. At present no other mode than that com- 

 monly practiced for inoculating the smallpox has been used 

 for giving the cow-pox; but it is probable this might be 

 varied with advantage. We should imitate the casual com- 

 munication more clearly were we first, by making the 

 smallest superficial incision or puncture on the skin, to pro- 

 duce a little scab, and then, removing it, to touch the abraded 

 part with the virus. A small portion of a thread imbrued 

 in the virus (as in the old method of inoculating the small- 

 pox) and laid upon the slightly incised skin might probably 

 prove a successful way of giving the disease; or the cutis 

 might be exposed in a minute point by an atom of blistering 

 plaster, and the virus brought in contact with it. In the 

 cases just alluded to, where I did not succeed in giving the 

 disease constitutionally, the experiment was made with 

 matter taken in a purulent state from a pustule on the 

 nipple of a cow. 



Is pure pus, though contained in a smallpox pustule, ever 

 capable of producing the smallpox perfectly? I suspect it 

 is not. Let us consider that it is always preceded by the 

 limpid fluid, which, in constitutions susceptible of variolous 

 contagion, is always infectious; and though, on opening 

 a pustule, its contents may appear perfectly purulent, yet a 

 given quantity of the limpid fluid may, at the same time, 

 be blended with it, though it would be imperceptible to the 

 only test of our senses, the eye. The presence, then, of this 

 fluid, or its mechanical diffusion through pus, may at all 

 times render active what is apparently mere pus, while its 

 total absence (as in stale pustules) may be attended with 

 the imperfect effects we have seen. 



It would be digressing too widely to go far into the 



