Some articles on testicle, bovine testicles:
Testosterone - History
... consisting of an extract of dog and guinea pig testicle ... Koch, established easy access to a large source of bovine testicles—the Chicago stockyards—and to students willing to endure the ceaseless toil of extracting their isolates ... derived 20 mg of a substance from a supply of 40 pounds of bovine testicles that, when administered to castrated roosters, pigs and rats, remasculinized them ...
... consisting of an extract of dog and guinea pig testicle ... Koch, established easy access to a large source of bovine testicles—the Chicago stockyards—and to students willing to endure the ceaseless toil of extracting their isolates ... derived 20 mg of a substance from a supply of 40 pounds of bovine testicles that, when administered to castrated roosters, pigs and rats, remasculinized them ...