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to the serum. To be effective the serum would have to be given before 
the disease had advanced to a diagnosable state. Such sera might be 
useful in cases where a patient well advanced in smallpox is discovered 
in an unvaccinated family. The unprotected ones in contact with such 
a case will probably be in the incubation stage of smallpox, and might 
be protected by injections of serum from a variola vera with exanthem. 
CONCLUSIONS. 
(1) The immunity which accompanies the development of a vaccine 
lesion on the skin of a monkey becomes manifest between the sixth and 
eleventh days. 
(2) After a variola lesion of the skin the immunity appears between 
the fifth and eighth days. 
(3) The organisms which produce this exanthem in variola imoculata 
in the monkey pass from the point of inoculation to the skin before the 
onset of the general immunity. 
(4) The development of an exanthem in variola inoculata in the 
monkey is not dependent upon a late development of the immunity re- 
action of the animal. 
(5) The use of variolicidal sera is indicated only in cases where it 
can be administered during the incubation stage of the disease. 
