In an experiment previously reported (1941) we were able to show little anthelmintic effect against the gastro-intestinal nematodes of sheep after using phenothiazine powder in single doses up to 0·3 gm. per Kg. body weight. In view of our experience and its contrast with that of many" other workers, we felt it desirable to test a much larger dose, to compare it with another brand of the drug, and (because of the very large variation in worm burden from lamb to lamb) to use not less than four lambs in each treatment group.

Accordingly, 12 lambs from a flock known to be naturally infested were purchased last November, and these were divided at random into three groups as follows: A, untreated controls; B, given compressed 5 gm. tablets of phenothiazine (recently placed on the market by a well-known firm) at the rate of 5 gm. per 5 Kg. body weight; and C, given phenothiazine powder in water as a drench, at the same dosage rate, with the addition to each dose of 1 gm. sodium glycocholate as a wetting agent. This powder was from the same batch as that used in our previous experiment. In each case the full amount was given as a single dose.

The same three criteria of efficacy were used as before: three eggcountings and lamb-weighings before and after treatment, and post mortem worm-counts. Eggs were counted by the same modified McMaster technique, the individual counts representing the eggs in 0·005 gm. of faeces, but on this occasion only three cells were counted per sheep per day.