670 ACTIVE IMMUNIZATION 



value of the method has been established, and it has been found the 

 greatest of all boons to the human race, and notwithstanding that it 

 has been definitely proved that a thorough and continuous practice 

 of the operation would quickly eradicate smallpox from the face of the 

 earth. This opposition is especially pernicious and unjust, since the 

 practice of former years of vaccinating by direct transmission from arm 

 to arm has been entirely abandoned, and that animal lymph, prepared 

 and collected under strict aseptic precautions, is being used exclusively. 



The Relationship of Variola and Vaccinia. The relationship of 

 variola to vaccinia has been discussed since Jenner's time, but no ade- 

 quate explanation has been found. 



According to the general belief the smallpox virus, whatever it may 

 be, is altered in its passage through a lower animal, and loses forever its 

 power of producing smallpox, but is still so closely related that the anti- 

 bodies it produces are sufficient to protect against smallpox. 



The close interrelationship existing between vaccinia and variola is 

 shown by the presence in the virus of both, and in section of the skin of 

 both, of microscopic cell inclusions, first described by Guarinieri in 1892. 

 This finding has been confirmed by Pfeiffer in Germany and Councilman 

 and his associates in this country. These investigators have made 

 extensive studies of these bodies, and believe them to be protozoa in- 

 timately associated with the etiology of vaccinia and variola. More 

 recently, Fornet has described certain small, diplococcus-like bodies 

 that were found in cowpox vaccine and in smallpox lesions. These are 

 regarded as having an etiologic relationship to smallpox, and if these 

 findings are confirmed, would prove the identity of variola and vaccinia. 



Recent investigators, particularly Copeman, of England, and Brink- 

 erhoff and Tyzzer, of America, have shown, by carefully conducted ex- 

 periments, that vaccination will protect monkeys against subsequent 

 inoculation with smallpox virus, and this completely confirms the early 

 experiments of Jenner and others who proved the efficacy of vaccination 

 by the "variolous test." 



The Preparation of Cowpox Vaccine. During the early days of 

 vaccination it was customary to inoculate human beings with material 

 obtained from the pustules of those previously vaccinated. The old- 

 time physician carefully removed choice scabs and carried them about 

 in a special case ready for inoculation. While this method served its 

 purpose well, there were several drawbacks to its use, the chief of which 

 was the danger of transmitting syphilis. It has now for many years 

 been the custom to use virus obtained from animals, the production of 



