H—29.

Preliminary observations on penicillin levels in milk have been conducted with a special procaine penicillin cerate preparation. The summarized results of studies on twelve quarters treated with 100,000 units of the special procaine penicillin cerate and 100,000 units of procaine penicillin cerate of the original batch, shown in Fig. 2, indicate that the special penicillin cerate was superior to the original batch in maintaining levels of penicillin in the milk, although it provoked lower concentrations up to the thirty-sixth hour.

Fig. 2—Penicillin Levels in Milk.

One injection of (a) 100,000 units of procaine penicillin cerate (batch 3/P.S.D E.P.D 12/1) per quarter; (b) 100,000 units special procaine penicillin cerate (batch 4 M.0.) per quarter. Daily milk yield of experimental cows 35-47 lb. , Averaged results from twelve quarters. Work has also been initiated on the distribution of penicillin in the lactating udder following the injection of the special procaine penicillin cerate product. Clinical Trials With Other Preparations : Small quantities of an aureomycin preparation (Lederle) and a dibromopropamidine isethionate-penicillin preparation became available during the year for clinical trials. A preliminary trial with a single injection of the aureomycin preparation in latent Str. agalactiae infection resulted in bacteriologica 1 sterilization of nineteen quarters of a total of twenty injected. Aureomycin may

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