A physician, aged 30, a graduate student, gave a positive reaction to the Schick test, Oct. 10, 1922. There was a very slight pseudoreaction. There was no history of previous diphtheria.
October 25, he carried out a virulence test with a culture from a known clinical case of diphtheria. At this date, he had not himself been in contact with a known clinical case for some time; nor had he been working with any other diphtheria cultures. While inoculating the guinea-pig, he pricked the skin on the dorsum of the terminal phalanx of the left thumb with the needle of a syringe containing the suspension from a twenty-four hour Loeffler slant. The suspension in the syringe was from a culture from the above mentioned case, and caused typical diphtheric lesions in the guinea-pig. October 29, the patient visited the laboratory and examined the inoculated animal, but after this date he