In a critical survey of the reports on experimental vaccination on human beings I attempted in 1926 to draw up some principles for carrying out an anti-tuberculous vaccination. Tentatively I began working along these lines and as the experiment seemed to turn out well I have continued along the path struck. In 1928 I published in The Journal a preliminary account of my experiments,1 and I now submit the results achieved up to the present.
The history of the production of the B C G vaccine is no doubt well known and I shall therefore content myself with mentioning that the vaccine is composed of an originally virulent strain of bovine tubercle bacilli, which by means of certain methods of cultivation has been made very nearly avirulent. To be approved, a vaccine of this kind should fulfil at least these two primary conditions: It should be free from any