The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.

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Naturally occurring or synthetic androgenic substances injected into adult rats shortly after hypophysectomy will cause varying degrees of tubular maintenance in the testes,'-5 but the interstitial cells are not prevented from undergoing After tubular atrophy in hypophysectomized rats has occurred, it has not been possible to restore spermatogenic activity by means of andro-gen~.'-~ Maintenance of spermatogenesis in hypophysectomized rats by androgens has not as yet been satisfactorily explained. The possibility that androgens have only an indirect effect on the germinal epithelium, scrota1 maintenance being of prime importance,s* has not been accepted by Nelson and M e r~k e l .~ Incontestable evidence that male hormones have a direct or only an indirect effect on spermatogenesis is still lacking.It has seemed of importance in view of our present lack of understanding with regard to the r d e played by androgens in spermatogenesis to study the effects of male hormones in immature hypophysectomized rats. This has seemed especially important since it has been shown that bull testis extracts' and andro~terone~ cause marked injury to the testicular tubules of young rats. The purpose of this investigation was to discover whether spermatogenesis would occur in immature hypophysectomized rats injected with androgenic substances. As we have never observed sperm heads, as described by Moore,' earlier than the 34th day of life, we selected animals much younger than this to rule out the possibility that sperm 1

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It has been shown1 that in parabiotic rats the testes of a hypophysectomized partner could be completely maintained in or restored to a normal condition by gonad-stimulating hormone emanating from the pituitary of a castrated twin. It was also reported that the pituitaries of cryptorchid and of normal partners were in this respect much less potent than those of castrates. The data which will be presented in this report for the most part confirm and extend the previous work.As regards the response of the testes of a hypophysectomized parabiotic twin it has been our experience that the following factors are of greatest importance in the final analysis: (1) The type of partner ; whether castrated (regardless of sex), cryptorchid, or normal.(2) The time necessary for adequate vascular anastomosis between the partners. (3) The time necessary for a physiological process to become manifest or to run to completion.Experience has shown that the scrotum in the rat reacts to testicular hormone much as do the accessory sexual organs.'. From the results of our former and present studies in parabiotic rats we have found it possible to conclude that the scrotum in a hypophysectomized parabiotic rat is qualitatively more sensitive to testicular hormone than are the prostate and seminal vesicles. This has proved to be an important criterion in our work on parabiotic rats, as a pair does not have to be sacrificed in order to discover from the condition of the accessory sexual glands and the interstitial cells of the testes whether or not testicular hormone is being produced. Further, our previous observations, confirmed by later results, have shown that within certain limits the size of the testes in a hypophysectomized parabiotic rat is an index to the degree of their gametogenic activity. This is especially true when the testes are large, since the interstitial tissue at best forms but a small fraction of the whole testis. For these reasons, the hypophysectomized