CHEMICAL MODIFICATION OF SPECIES DIFFERENCES IN THE PITUITARY

Among the factors requiring careful evaluation in endocrine research, species variability is one of the most important. Different animals may vary greatly in their response to an endocrine principle, and an extract derived from an organ of one species may produce a different effect in a test animal from that produced by an extract of a homologous organ of another species. Much confusion exists because of failure in many instances to recognize this source of error. This is perhaps best exemplified in the recent contributions to the physiology of the pituitary and the gonads.¹ Clinical applications of animal experiments have been made in the expectation that the human being would respond in the same manner as the animal in which a particular extract was assayed. That this is by no means always the case is now attested by much evidence.¹ Conversely, similar extracts derived from different species are often