270 APPLIED IMMUNOLOGY 



Characteristics of Vaccinia Sites. — Due to trauma 

 alone, a few minutes after vaccination the skin im- 

 mediately surrounding the wound assumes a reddish 

 line ; this disappears in a few hours. If at the end of 

 twenty-four hours the vaccinated spot exhibits an 

 areola, with or without papule, one-half centimetre or 

 more in diameter, which inflammatory zone decreases 

 in seventy-two hours, it is to be regarded as an al- 

 lergic reaction of immunity due to specific antibodies 

 in the individual and excuses him from fm'ther im- 

 mediate vaccination. If the areola observed at the end 

 of twenty-four hours develops into a small vesicle 

 maturing on the fifth or sixth day, then rapidly sub- 

 siding, it is to be regarded as a case of vaccinoid, that 

 is, one where, although antibodies are not present, the 

 power to form them exists from previous vaccination. 

 If reactionary changes, characterized by a reddened, 

 inflammatory, indurated areola or aula surrounding 

 a papule, supervened only from the second to the fifth 

 day, followed by flattening of the smnmit of the 

 papule, it is to be regarded as a case of typical vac- 

 cinia. By the tenth day the reaction will have reached 

 its maximum, the inflammatory areola measuring 

 sometimes more than five centimetres and the papule 

 as much as one centimetre. The papilla at the onset 

 assumes a pale pinkish-gray color, changing to a gray- 



