108 Such wholesome instruction and religious training in regard to Christian marriage will be quite different from that exaggerated physiological education by means of which, in these times of ours, some reformers of married life make pretense of helping those joined in wedlock, laying much stress on these physiological matters, in which is learned rather the art of sinning in a subtle way than the virtue of living chastely.
Source: Casti Connubii (Vatican.va)