a biodegradable polymer is provided for use in providing syringeable , in - situ forming , solid biodegradable implants for animals . the polymer is placed into the animal in liquid form and cures to form the implant in - situ . a thermoplastic system to form said implant comprises the steps of dissolving a non - reactive polymer in biocompatible solvent to form a liquid , placing the liquid within the animal , and allowing the solvent to dissipate to produce the implant . an alternative , thermosetting system comprises mixing together effective amounts of a liquid acrylic ester terminated , biodegradable prepolymer and a curing agent , placing the liquid mixture within an animal and allowing the prepolymer to cure to form the implant . both systems provide a syringeable , solid biodegradable delivery system by the addition of an effective level of biologically active agent to the liquid before injection into the body .