Effect of route of administration on the bioassay of prolactin

In young pigeons of the same age and race the response of the crop-glands to prolactin administered by 5 different routes has been studied and found to differ widely. Subcutaneous and intracutaneous injections are about 11 times as efficient as intravenous injections, about 5 times as efficient as intramuscular injections, and about 8 times as efficient as intraperitoneal injections at the dosage level used