Coopers Animal Health Limited

Peter H Marsden

Rodney C Baker

Michael T Shepherd

A bolus for releasing a biologically active substance into a liquid environment according to this invention comprising an elongate core, at least one end of which is frustoconical and a liquid impervious casing at one end and open at the other disposed about the core, the bolus being so constructed that, in use, the casing is progressively shed as the core retreats, thereby releasing the active substance at a rate which varies over at least one time period, the casing being so structured as to retain its integrity without disintegrating in the absence of any support provided by the core.

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Berkhamsted, United Kingdom

Peter H Marsden