1. A peptone salt agar appears to be the medium of choice in the preparation of suspensions of V strains of B. typhosus for Vi agglutination. The presence of heart extract may have a definite inhibitory effect on Viagglutination but the effect is irregular.
2. A safe method for the preparation of anti-Vi serum with virulent cultures is described.
3. Repeated endeavours to produce an anti-Vi serum by the use of formolized vaccines were unsuccessful.
4. A suspension of a V strain killed at 55° C. can be used as a vaccine for producing Vi agglutination.
5. The thermostability of the Vi antigen is discussed.
6. An analysis is made of the presence of Vi antigen in a number of freshly isolated and stock strains of B. typhosus.
7. A series of typhoid cases has been examined for Vi agglutination, and it is concluded that the latter is unlikely to be of any clinical value either in diagnosis or prognosis.
Acknowledgements. The writer wishes to express his thanks to his colleagues, Dr R. M. Humphreys, Senior Physician, Khartoum and Dr J. S. Hovell, Omdurman, for their valuable co-operation; and to Dr Ali Bedri, Khartoum Hospital, he is much indebted for assistance in analysing the clinical data and records of the typhoid cases.