LABORATORY DIFFERENTIATION OF SMALLPOX AND CHICKENPOX

TIECHE NOTED in 19071 the phenomenon previously described by Jenner, namely that the application of material from a smallpox vesicle to the scarified skin of an immune person will cause a constant reaction similar to the Pirquet tuberculin skin reaction. In 10 years' experience in making tests upon himself, Tieche found the test accurate in 98 per cent of the instances. In 1915, Force and Beckwith2 published results upon a similar method of procedure but using immune rabbits instead of persons. Specimens from the vesicles of 6 cases of smallpox gave marked reactions, while similar specimens from 6 cases of chickenpox gave no reactions. In 1921, Leake and Force3 proved the identity of alastrim and smallpox by this method. Chickenpox material gave consistently negative results while smallpox crusts, alastrim material and vaccine virus produced positive intracutaneous reactions on rabbits previously immunized with vaccine virus. Defries and Hanna4 tested in a similar manner material from 75 patients in a smallpox epidemic. Sixty gave positive reactions, 5 negative and 10 unsatisfactory. The authors state that " these laboratory findings were confirmed by the subsequent history of the cases in the majority of instances." In our study more than 650 tests were made upon rabbits, guinea pigs, rats and man, using vaccine virus from various manufacturers and material obtained