On the other hand, the existence of a number of cases of insanity in a family may be due to external or accidental causes, and not indicate any general taint. It is true that there are families in which insanity occurs where the allied neuroses do not often appear, and that various diseases of the nervous system may be frequent in a stock in which insanity is rare or absent. A person who has recovered from an acute attack of cerebro-mental disorder, if previously healthy and without hereditary predisposition to such diseases, may marry and not transmit to offspring either insanity or any of its allied diseases, while it is not uncommon for an individual seemingly the least liable to mental disease of a whole family to become insane, leaving several brothers and sisters with ill-balanced minds to get through life without breaking down, the morbid energy in the latter case expending itself in irregularities of conduct and of mental operations as fast as it is created, instead of being stored up for {115} occasional outbreaks. The degree to which insanity may be expected to follow any given antecedents can only be estimated very approximately, as the laws of heredity are very little known, and as there is a tendency in nature, so strong that it is constantly asserting itself, to return to the healthy type if it has a chance. But, in general, it may be said that the more individuals of both branches in whom insanity and its allied diseases are found, just so far may a larger proportion of the children be expected to suffer. The character of the particular disease or tendency to disease which is likely to develop from any given antecedents is still a very obscure matter. But the case is often clear enough to justify the remark that if childhood has any rights it has the right to be born healthy.