It has been assumed that diabetes, which renders men impotent, is competent also to cause sterility in women. Hofmeier reports a case which appears decisive on this point. In a woman 20 years of age, who had menstruated regularly since she was 14 until a year previously, when the flow had ceased, he found the uterus extremely small, barely 5 cm. (2 in.) in length, extremely atrophied, the ovaries also atrophied and very small; the urine contained large quantities of sugar. Here was doubtless a case of atrophy of the reproductive organs secondary to diabetes.
In England, where the excessive use of alcohol is observed very frequently in women as well as in men, sterility has frequently been regarded as a result of chronic alcoholism. Matthews Duncan reports cases which lead to the belief that alcohol has a specifically deleterious effect upon fertility. Apart from the general or constitutional disturbances dependent upon the abuse of alcohol, this agent has in many cases a well-recognized pathogenic influence upon the female reproductive organs, the morbid condition which is most frequently and most readily assignable to this cause being chronic oophoritis. The obesity which so frequently results from alcoholic excess is a contributory cause of sterility.
Certain drugs, more especially quinine and morphine, are reputed to cause sterility. Davies, reviving an old opinion, considers that of all drugs tannin is the most effective in leading to sterility, and he considers tea-drinking as responsible for this effect.
The influence of certain cerebral affections and psychical disorders in checking ovulation has been established. Thus, de Montyel has recently shown that in families subject to hereditary mental disorders, there is an unusually large proportion (1 : 7) of barren marriages.
In addition, there are many influences which are known to prevent or to diminish ovulation in the case of the lower animals, and which may therefore be assumed with considerable probability to have a similar effect in women. More especially we are here concerned with external influences affecting unfavourably nutrition and innervation, and therewith also ovulation; also near kinship between the parties to the act of intercourse; and finally hereditary predisposition. In animals, captivity, exposure to cold, over-exertion, insufficient or unsuitable food, and inbreeding, have been proved to result in infertility.
Doubleday asserted that “a too abundant supply of nutriment hinders reproduction, whereas on the other hand insufficient or improper food favours reproductive activity and increases the number of the offspring.” Spencer, however, rightly points out that the infertility noticed in these circumstances is not the direct result of prosperity, but depends upon the pathological obesity which is thus engendered by overfeeding.
No less interesting are the observations that have been made regarding sterility in animals in confinement. In such animals there are wide differences. Some refuse to cohabit, or have lost sexual desire; others, again, show excessive sexual desire and cohabit too often, without any result; or even if fertilization occurs, abortion often ensues. In yet other cases, though conception follows intercourse, and the animals go on to full term before delivery, the young are still-born, or are weakly and misshapen. Caged birds often lay no eggs at all or very few; or if they do lay, they neglect their eggs; or if incubated, the eggs fail to hatch out. In France, experiments regarding this matter were made with domestic fowls. If the hens were given great freedom, 20 per cent only of the eggs remained unhatched; with less freedom, 40 per cent of the eggs were failures; whilst if the fowls were kept in a coop, 60 per cent of the eggs were unhatched.
“Convincing proofs,” writes Darwin, “have been obtained to the effect that wild animals which have recently lost their freedom have their fertility diminished to a most remarkable extent. This infertility is not dependent upon any degeneration of the reproductive organs. There are many animals of the most diverse species, which, whilst they copulate freely in confinement, fail in these circumstances to conceive; others again, even if they conceive and have living young, give birth to these in numbers which are unquestionably much smaller than would be the case were the parents in the free state.”
Interesting observations have been made by pigeon breeders. They state that when pigeons brought up in the same nest pair, the number of their offspring is usually very small.
The influence upon fertility of unfavourable conditions of temperature, either excessive heat or excessive cold, is very great. In the case of pigeons, for instance, if the pigeon cot is adjacent to the heated wall of a dwelling house, the pigeons sometimes begin to lay as early as January, and may have young as often as eight times in a single year. When the dovecot is cold, on the other hand, the number of broods is smaller. In general, the procreative capacity is greater in summer than in winter.