Extract During the early 1950s, whilst the writer was in practice in Kenya, the need for some simple, practical method of picking out cows infected with brucellosis was recognized. Whatever test was used had to be applicable to as large a proportion of the female herd as possible, had to be simple to perform, requiring little laboratory technique or equipment, and had to be at least as reliable as the whey-plate, or blood-serum tests. The necessity for such a test was brought about by the fact that the only diagnostic laboratory in the country was at Kabete, some 250 miles away. Any material sent there was liable to deteriorate en route and the average delay of ten days before a report could be expected made such a field test desirable. This condition also applies here in Northland at the present time.