212 MICEOBES, FEEMENXS, AND MOULDS. 



It may be useful to retrace liere the curious history 

 of vaccine, since it is directly interesting to us aH 



o 



O .. 



o 



d •: . 



'■■?■■ 



'^efi% 



Fig. 91. — Section of sTdn covering a Bmall-pox pustule, a, horny layer of the 

 epideTmlB; d, adenoid tisBue.; m, m, micrococci stained with methyl violet (x 

 860 diam.)* 



Before vaccine was discovered, inoculation with 

 small -pox was practised as a preventive measure. 



