National Vaccine Establishment. 309 



It continues out for a day or two, and then begins to 

 fade ; sometimes forming two or three concentric circles. 



After the areola is formed, the vesicle begins to decline ; 

 the centre first turns brown, and the whole gradually changes 

 into a hard smooth scab, of a very dark' mahogany colour. 

 This dry crust usually drops off about the end of the third 

 week, leaving a permanent cicatrix. 



Varieties in the Progress and Appearance of the Vaccine Ve- 

 sicle, not preventing the Success of Vaccination. 



The first appearance is seldom earlier, but often later 

 than has been described. In some rare instances the vesicle 

 commences even a fortnight or three weeks after vaccina- 

 tion ; but if the process is then regular, it is equally effica- 

 cious. 



When the vesicle is slightly ruptured before the sixth 

 day, if it resume its proper form, and the process continue 

 quite regular, success is not prevented : nor is it, when the 

 crust of a regular vesicle is rubbed off in the decline of the 

 disease. 



The irregular and imperfect Vesicle and Pustule, which are 

 not to he depended upon. 



In these deviations there is usually a premature itching, 

 irritation, inflammation, vesication, or suppuration. Or 

 the' progress of the vesicle is too rapid, its texture soft, its 

 edge not well defined, its centre elevated, and the contents 

 discoloured or purulent. Or instead of a proper areola, a 

 premature efflorescence of a dusky purple hue takes place, 

 and the scab is of a light brown or amber colour. 



The irregular vesicle or pustule is more liable to be broken 

 than the other, both from its more pointed form and softer 

 texture, and also from its being usually so irritable as to 

 provoke scratching. When broken, or even without this 

 happening, ulceration often ensues. 



A vesicle, apparently regular at first, sometimes does not 

 augment to the proper size, but dies away without com- 

 pleting the regular process. This usually leaves no cicatrix, 

 or one which is almost imperceptible. 



When those, or any other considerable deviation from 

 the regular course of the disease take place, no dependence 

 can be placed upon the operation. In such cases vaccina- 

 tion should be repeated. 



Probable Onuses of irregular Vesicles and Pustules. 

 These accidents may be occasioned by matter or Ivinph 

 being taken from an irregular vesicle or pustule at any pe- 

 riod, or from a regular vesicle at too late a period ; or by 



U 3 lymph 



