A simple method of photographing Ouchterlony plates.

one which is now widely used for diagnostic purposes. The difficulties involved in making a permanent accurate record of the results, an essential part of the technique, are indicated by the variety of photographic methods that have been used, the majority of which are time-consuming and involve the use of special photographic equipment. We have been using a modification of a method first described by Bartlett (quoted by Gibson, 1954) which is accurate, rapid, and requires a minimum of equipment. This technique consists essentially of making a photogram of the agar plate on a lantern plate. Because of its simplicity it is of value to those using the gel-diffusion technique.