But in spite of all this these statistics are entitled, as much as analog ous conditions in the animal and plant worlds, to a high value. They remind us that, in the estimation of the causes of sterility, we should not confine ourselves to local disturbances, but should search for them also in constitutional conditions, which again are very often produced by exter nal hifluences.
It is strange that we so seldom pursue the path which most certainly leads to the explanation of the etiological relations of the diseases, and that we have not attempted to determine the causes of sterility by anatomi cal investigation. In fact until recent times the part played by patho logical anatomy in this respect has been a very unimportant one. This is easily explained Above all things at autopsies there is not that desirable attention paid to the female genital organs, which are deeply buried in the pelvis, while the male genitals are, as a rule, absolutely unheeded; it is on this account that a great number of anatomical lesions that occasion sterility do not appear very noteworthy, and that the investigation of the genital parts for causes of stenlity belongs to the more subtle propositions. Further, unfruitfulness is an affection that does not lead to death. If a sterile person dies, the autopsy is only made on account of the intercurrent dis ease which has caused death. The conditions found at the autopsy are often misleading; they must be judged with great care, for many previ ously existing lesions may disappear at the climacteric period, or anatomi cal changes then for the first time appear which may s9em to have existed previously as causes of sterility, and may lead to false explanations. Sys tematic investigations upon corpses directed to the consideration of the causes of sterility, are,.therefore, somewhat questionable, because they are usually made upon persons whose sexual capability during married life is unknown. The relation between anatomical change and physiological can by no means be determined with any great certainty from this material. Still such investigations, as those conducted by Winckel in 150 cases, and by Beigel in 600 cases, for the discovery of the causes of sterility in the female, are very valuable, even though they serve only to show the great variety and equal implication of the whole female genital tract in the anatomical causes of sterility Of still greater importance are those in vestigations of the male genitals, which have been conducted chiefly by A. Schlemmer and A. Busch with such admirable results.
Notwithstanding the surprising results in the explanation of the causes of disease derived from experimental pathology, it is noteworthy that as yet no attempt has been made to solve the question of the causes of sterility by experiments upon animals. Many of the mechanical hin drances could probably 139 easily produced, and their influence, on account of the ease with which copulation can be regulated, could easily be proven. Up to the present time only a few such experiments have been made, and these have only an indirect-bearing upon the study of sterility.
The study of the unfruitfulness of both sexes rests principally upon. the broad foundation of clinical observation and experience, though this basis is not to be regarded as a very certain one, and we will later on, when speaking of the diagnosis and therapeutics, learn why too much de pendence cannot be placed on such material. With this uncertainty, a searching, sceptical investigation is doubly called for.
We have already shown how markedly the fertility of plants and animals may be influenced by external influences, either natural or arti ficial. This change is, as we have seen, a varied one; it consists partly of a diminution of the fertility, which may be increased to absolute sterility. 'The human species is no exception, as it too is subject to the influences of the external world. As by long-continued influences a gradual change is effected upon large bodies of people, so may unfavorable external factors, which act more suddenly and in a more violent manner upon individuals, exert a weakening or disease-producing action upon the bodily constitution. The bodily constitution altered in this manner, is then again predisposed to exert a harmful influence upon the structure and function of single organs. In this way—weakening of the constitu tion and diseases of organs –eertain external influences act upon the pro creative capability.
But surely this action is exerted in the human species in a lessened degree. Of the external influences mentioned above, which act in such an unfavorable manner upon the fertility of plant and animal organisms, many are not to be taken into consideration when speaking of the human species; I point only to the arbitrary coupling. To others the humau species seems to accommodate itself, or at least to successfully shield itself from them, so that external cosmic influences, particularly in respect to sexual relations, are not in a condition to affect it except in a lesser degree. Opposed to this in the human species, in contradistinction to other organ isms, there is present another factor, which certainly acts more powerfully than the cosmic influences, namely, civilization. Our social conditions are not without influence upon fertility, and are certainly in their conse quences often causes of unfruitftdness.
Less often does it occur that the reason for married sterility is to be sought in different defects of both of the married pair, but in the majority of cases this is dependent upon the procreative incapability of one or the other of the married pair. The causes of sterility are, however, different in the two sexes, and require hence a separate description. I will, there fore, first speak of the causes of unfruitfulness in the female, which are surely the most important, and will afterwards speak of the causes in the male. In speaking of the causes of sterility in the female, I shall use the division repeatedly emphasized; but when speaking of the male, for prac tical reasons, I will depart from that division.