Abstract
Plerocercoid larvae of the tapeworm, Spirometra mansonoidas, produce a substance which stimulates growth in laboratory rodents. Plerocercoid growth factor (PGF) can be collected in vitro by incubating larvae is buffered saline at 30°C. This report describes a procedure by which active PGF was isolated by polyacrylamide gel electrophoresis and identified by the pigeon crop sac assay.