Vaccination 95 



ease that achieves the" result, and if the operation be improperly 

 done, poor i.e., old or inert matter introduced, or if after intro- 

 duction it be destroyed by the application of antiseptics, no effect 

 can be expected. Hence all persons that have been vaccinated may 

 not have had vaccinia, the essential condition leading to immunity. 

 Nor does the occurrence of a local lesion act as a guarantee that 

 vaccinia has been induced. Careful examination of the resulting 

 lesions should always be made, that the type of the infection may be 

 studied. It is the disease, vaccinia, that must occur three days' 

 incubation, three days' vesiculation, three days' pustulation, and 

 subsequent cicatrization with the formation of a punctate scar. 



An arm may be made very sore, may suppurate or even become 

 gangrenous, without vaccinia having occurred or the desired benefit 

 attained. 



The accidents of vaccination were formerly numerous and some- 

 times disastrous because of the general inattention to the quality 

 of the materials used, the mode of inserting them, the condition of 

 the patient's skin, and the careless treatment of the resulting lesions. 

 When human virus was used, that is, matter taken from a vaccinia 

 lesion from a human being, the transmission of human diseases, 

 such as syphilis and erysipelas, occasionally took place; now these 

 are rare accidents indeed, because no virus is employed except 

 that taken from carefully selected and treated calves or heifers. 

 When no attention was paid to the quality of the bovine virus, and 

 no governmental inspection of laboratories required, the accidental 

 contamination of the virus occasioned a small number of accidental 

 infections of the wound. There are a good many cases of phlegmon, 

 gangrene and tetanus in the older literature. But these evils are 

 becoming less and less as greater attention is given to the selection 

 and preparation of the virus. Some accidents and some few deaths 

 there will probably always be, just as there are occasional accidents 

 and occasional fatal results following all kinds of trivial injuries, 

 though care will eliminate them as the sources of accident are bet- 

 ter understood. 



3. Pasteurian vaccination or bacterination: Although the word 

 vaccination is derived from the Latin vacca, "a cow," and was first 

 employed in connection with Jenner's method of introducing virus 

 modified by passage through a cow, Pasteur, in honor of Jenner, 

 applied it to every kind of protective inoculation, and the word 

 bacterination is only introduced for the purpose of indicating certain 

 differences in the method. 



In 1880 Pasteur* observed that some hens inoculated with a cul- 

 ture of the bacillus of chicken cholera that had been on hand for 

 some time did not die as was expected. Later, securing a fresh and 

 virulent culture, these and other chickens were inoculated. The 

 former hens did not die, the new hens did. Quick to observe and 

 * "Compte rendu de la Soc. de Biol., 1880, 239; 315 et seq. 



