Experimental and clinical evidence, as well as numerous studies of transplantations, indicates clearly that the testes possess one or more endocrine functions. The experimental evidence of the presence of an internal secretion of the testes has been based primarily on the effects observed on the removal of the testes. Although it has been stated from time to time that extracts of testicular tissue when injected into castrated animals produce various effects, many of which are associated with secondary sex characters, most workers in endocrinology have not accepted these statements because the criteria used for determining the effects of the extracts on castrated animals were of doubtful value. Probably the first report giving clear cut evidence of extracting and fractionating the hormone from testis tissue was given by McGee,1 who obtained a lipin fraction from bull's testis which, when injected intramuscularly into brown leghorn capons, caused a remarkable growth of
THE TESTICULAR HORMONE. JAMA. 1932;98(9):738–739. doi:10.1001/jama.1932.02730350052014
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