EXANTHEMATA 



125 



inoculation with cow-pox virus protects against small- 

 pox, and vice versa, and the same protective action 

 holds in man. This has been proved for more than a 

 century — i. e., since Jenner, in 1796, introduced vaccina- 

 tion. In cA^ery country where vaccination has been made 

 compulsory there has been a sudden and constant lower- 

 ing of the number of small-pox cases, and those which do 

 occur are of a milder nature than formerly. 

 The best method of vaccinating is as follows: 

 Carefully clean the outer surface of the arm with soap 

 and water, followed by alcohol. Do not paint the sJiin 

 with iodin. Two 

 or three drops of 

 vaccine virus are 

 now placed on the 

 dry skin, an inch 

 apart. With a 

 sharp, sterile 

 needle two or three 

 parallel linear cuts 

 or scratches an 

 inch long are made, 

 each scratch be- 

 ginning in a drop 

 of vaccine virus. 

 With the fiat of 

 the needle the virus 

 is then rubbed 

 gently into the scratches. The vaccinated area is allowed 

 to dry. No dressing should be applied, experience having 

 shown that the various shields often do more harm than 

 good, for they retain heat and moisture. The illustration 

 shows a linear vaccination made as here described. 



Fig. 40. — Linear vaccination. The erup- 

 tion on the eleventh day. (From Rosentiu, 

 " Preventive Medicine and Hygiene.") 



