VACCINATION AGAINST SMALLPOX 219 



tention. In the cases alluded to here you will observe that 

 the removal from the original source of the matter had 

 made no alteration or change in the nature or appearance 

 of the disease, and that it may be continued, ad infinitum 

 (I imagine), from one person to another (if care be ob- 

 served in taking the matter at a proper period) without 

 any necessity of recurring to the original matter of the 

 cow. 



" I should be happy if any endeavours of mine could 

 tend further to elucidate the subject, and shall be much 

 gratified is sending you any further observations I may 

 be enabled to make. 



" I have the pleasure to subscribe myself, 

 "Dear sir, etc., 



"JOSEPH H. MARSHALL. 



" EASTIWCTOK, GLOUCESTERSHIRE, April 26, 1799." 



The gentleman who favoured me with the above ac- 

 count has continued to prosecute his inquiries with un- 

 remitting industry, and has communicated the result in an- 

 other letter, which at his request I lay before the public 

 without abbreviation. 



Dr. Marshall's second letter: 



"DEAR SIR: 



" Since the date of my former letter I have continued 

 to inoculate with the cow-pox virus. Including the cases 

 before enumerated, the number now amounts to four hun- 

 dred and twenty-three. It would be tedious and useless 

 to detail the progress of the disease in each individual 

 it is sufficient to observe that I noticed no deviation in any 

 respect from the cases I formerly adduced. The general 

 appearances of the arm exactly corresponded with the ac- 

 count given in your first publication. When they were 

 disposed to become troublesome by erysipelatous inflam- 

 mation, an application of equal parts of vinegar and water 

 always answered the desired intention. I must not omit 

 to inform you that when the disease had duly acted upon 

 the constitution I have frequently used the vitriolic acid. 

 A portion of a drop applied with the head of a probe or 



