SMALLPOX AND VACCINIA 575 



area, varying from a square centimeter to nearly twice that size. The 

 crust that forms over such a wound furnishes excellent anaerobic 

 conditions for the growth of bacteria, and the thickness of the crust 

 offers mechanical opposition to the formation of the vesicles, which 

 are prone to appear around the area in consequence. Vaccination by 

 scarification is forbidden by law in Germany. 



2. The Course of the Disease, Vaccinia. The initial reddened site 

 of inoculation soon disappears, leaving only a small scratch or punc- 

 ture; about the third or fourth day, however, one or several small 

 bright red papules appear, which become vesicular by the end of 

 seven days and surrounded with a bright red areola. The contents 

 of the vesicle become yellowish, usually from the eighth to the tenth 

 day, and discharge a yellowish fluid if they are opened. The contents 

 then become dessicated, and a crust forms which drops off in about 

 two weeks. 



From the third to the fifth day after the vaccination a febrile 

 reaction of one or two degrees is usually experienced, and the site of 

 the vaccination itches intensely and is painful. There is frequently 

 loss of appetite and general symptoms of malaise quite out of propor- 

 tion to the amount of local reaction. By the end of the second week the 

 symptoms have disappeared and the sunken multilocular scar is the 

 principal residual evidence of a successful vaccination. It is generally 

 believed that already by the ninth to the eleventh day after inoculation 

 the patient is relatively refractory to infection with smallpox virus. 



3. Immunity. The duration of immunity is not definitely known, 

 but it is stated to be from seven to ten years on the average. In Ger- 

 many, where vaccination has been enforced by law for five decades, 

 a child is required to be vaccinated by the end of the first year, again 

 about the time it enters school, and a third time at the age of sixteen 

 or thereabouts. 



Occasionally a first vaccination is unsuccessful. Frequently old or 

 inactive vaccine, poor technic, or a deliberate sterilization of the 

 vaccined area with disinfectants are responsible, because man does 

 not, as a rule, exhibit immunity to natural vaccinia. Several suc- 

 cessive negative results should be obtained before the individual is 

 pronounced refractory. 



4. Revaccination. Revaccination frequently does not lead to a 

 "take," but in a fair proportion of individuals a typical reaction may 

 take place; this may be an accelerated reaction. The accelerated 

 reaction runs a more rapid course than the ordinary reaction and 



