The positive action of semen, or rather of the testicular products, has been much investigated during recent years, and appears on the whole to be demonstrated. The notable discovery by Brown-Séquard, a quarter of a century ago, that the ingestion of the testicular juices in states of debility and senility acted as a beneficial stimulant and tonic, opened the way to a new field of therapeutics. Many investigators in various countries have found that testicular extracts, and more especially the spermin as studied by Poehl,[[140]] and by him regarded as a positive katalysator or accelerator of metabolic processes, exert a real influence in giving tone to the heart and other muscles, and in improving the metabolism of the tissues even when all influences of mental suggestion have been excluded.[[141]]
As the ovaries are strictly analogous to the testes, it was surmised that ovarian extract might prove a drug equally valuable with testicular products. As a matter of fact, ovarian extract, in the form of ovarin, etc., would seem to have proved beneficial in various disorders, more especially in anæmia and in troubles due to the artificial menopause. In most conditions, however, in which it has been employed the results are doubtful or uncertain, and some authorities believe that the influence of suggestion plays a considerable part here.
There is, however, another use which is subserved by the testicular products, a use which may indeed be said to be implied in those uses to which reference has already been made, but is yet historically the latest to be realized and studied. It was not until 1869 that Brown-Séquard first suggested that an important secretion was elaborated by the ductless glands and received into the circulation, but that suggestion proved to be epoch-making. If these glandular secretions are so valuable when administered as drugs to other persons, must they not be of far greater value when naturally secreted and poured out into the circulation in the living body? It is now generally believed, on the basis of a large and various body of evidence, that this is undoubtedly so. In a very crude form, indeed, this belief is by no means modern. In opposition to the old writers who were inclined to regard the semen as an excretion which it was beneficial to expel, there were other ancient authorities who argued that it was beneficial to retain it as being a vital fluid which, if reabsorbed, served to invigorate the body. The great physiologist, Haller, in the middle of the eighteenth century, came very near to the modern doctrine when he stated in his Elements of Physiology that the sperm accumulated in the seminical vesicles is pumped back into the blood, and thus produces the beard and the hair together with the other surprising changes of puberty which are absent in the eunuch. The reabsorption of semen can scarcely be said to be a part of the modern physiological doctrine, but it is at least now generally held that the testes secrete substances which pass into the circulation and are of immense importance in the development of the organism.
The experiments of Shattock and Seligmann indicate that the semen and its reabsorption in the seminal vesicles, or the nervous reactions produced by its presence, can have no part in the formation of secondary sexual characters. These investigators occluded the vas deferens in sheep by ligature, at an early age, rendering them later sterile though not impotent. The secondary sexual characters appeared as in ordinary sheep. Spermatogenesis, these inquirers conclude, may be the initial factor, but the results must be attributed to the elaboration by the testicles of an internal secretion and its absorption into the general circulation.[[142]]
When animals are castrated there is enlargement of the ductless glands in the body, notably the thyroid and the suprarenal capsules.[[143]] It is evident, therefore, that the secretions of these ductless glands are in some degree compensatory to those of the testes. But this compensatory action is inadequate to produce any sexual development in the absence of the testes.
We see, therefore, how extremely important is the function of the testis. Its significance is not alone for the race, it is not simply concerned with the formation of the spermatozoa which share equally with the ova the honor of making the mankind of the future. It also has a separate and distinct function which has reference to the individual. It elaborates those internal secretions which stimulate and maintain the physical and mental characters, constituting all that is most masculine in the male animal, all that makes the man in distinction from the eunuch. Among various primitive peoples, including those of the European race whence we ourselves spring, the most solemn form of oath was sworn by placing the hand on the testes, dimly recognized as the most sacred part of the body. A crude and passing phase of civilization has ignorantly cast ignominy upon the sexual organs; the more primitive belief is now justified by our advancing knowledge.
In these as in other respects the ovaries are precisely analogous to the testes. They not only form the ova, but they elaborate for internal use a secretion which develops and maintains the special physical and mental qualities of womanhood, as the testicular secretion those of manhood. Moreover, as Cecca and Zappi found, removal of the ovaries has exactly the same effect on the abnormal development of the other ductless glands as has removal of the testes. It is of interest to point out that the internal secretion of the ovaries and its important functions seem to have been suggested before any other secretion than the sperm was attributed to the testes. Early in the nineteenth century Cabanis argued ("De l'Influence des Sexes sur le Caractère des Idées et des Affections Morales," Rapport du Physique et du Moral de l'Homme, 1824, vol. ii, p. 18) that the ovaries are secreting glands, forming a "particular humor" which is reabsorbed into the blood and imparts excitations which are felt by the whole system and all its organs.