The causes of mania are not always so distinctly traceable as those of melancholia. Heredity is an important factor. This is, however, not so much a question of actual direct inheritance of mental disturbance from the preceding generation, as a family trait of mental weakness that can be traced through many generations. Direct inheritance of acquired peculiarities no scientific thinker now admits. Family peculiarities, however, are traceable through many generations. So striking a peculiarity as the possession of six fingers or six toes has been traced through a majority of the members of as many as five generations in a single family. And as has been said other family traits can be traced back in the same way.
It would not be entirely surprising, then, if mental peculiarities and a predisposition to mental disturbance should be also a matter of inheritance. It is well known now that the physical condition of the brain substance may have much to do with the intellectual functions. Injuries to certain parts of the brain may cause special changes even of personal disposition. In the famous crowbar case, in which an iron drill over four feet in length was driven through one side of the head, it was noted that the man, who had been somewhat morose before, was inclined to be more amiable afterwards, but also had a tendency to be bibulous in his habits.
German clinicians have recently pointed out that the existence of an excess of pressure on the frontal lobes of the brain, such as is produced by the presence of a tumour, may cause a tendency to make little jokes. This symptom is known as "Witzelsucht." It is considered of distinct significance and value in localising tumours of the brain. The question of the type of the witticisms and particularly a tendency to obscenity are noted as a special diagnostic aid in the recognition of the character of these tumours by at least three prominent German medical observers.
If modifications of the brain substance can produce changes of disposition and temperament, it is easy to understand how temperament and disposition may be a matter of inheritance. If we inherit a father's nose and a mother's eyes, [{225}] the minutest conformations of brain substance may also be inherited. It is on these, to a certain extent at least, that the general outlines of the disposition depend. It would not be surprising to find, then, a disposition to mental unsteadiness as the result of the transmission of brain peculiarities. Here, as in everything else, there is question, not merely of parental influence, but of the inheritance of the family traits, some of which are skipped in certain generations.
When melancholia and mania are said to be due to heredity as one of the principal causes, the meaning intended is that in certain families the brain tissues are liable to be transmitted in somewhat impaired condition, and that through these brain tissues the mind will either not act properly, or under the stress of violent emotion, the loss of friends by death, or the loss of fortune, or serious disappointments in life, or a love affair, the already tottering mental condition will be overturned. In a word, it is not the direct transmission of insanity, but of a predisposition to the development of insanity under stresses and strains that is a matter of family inheritance. This is considered true now not only of mental but of all diseases. Not consumption, but the predisposition to it is inherited.
These considerations make clear how important this matter of heredity is. Physicians and students of anthropology are so much concerned about the increase of insanity as the result of the intermarriage of defectives that we are constantly reading in the newspapers of attempts at the legal regulations of marriage, so as to prevent further racial degeneration. Under present circumstances, any such legal regulation is probably impossible; but it seems perfectly clear that clerical influence should be brought to bear to discourage, as far as possible, intermarriage among those of even slightly disturbed mental heredity. Especially must any such idea as the possible beneficial influence of matrimony (for there are popular traditions to this effect) be unhesitatingly rejected and it must not be allowed to tempt those interested to look on such intermarriage with indifference.
Another and more serious question for the clergyman is that of the vocation in life of those who are weak mentally. By vocation is meant not only religious calling, but the occupation in life generally. Young people of unstable mentality and especially those of insane heredity should be advised against taking up such professions as that of actor or actress, or broker, or other life duties that entail excitement and mental strain. As far as possible they should be discouraged from taking up city life, and should be advised to live quietly in the country.
Mania is apt to follow certain severe infectious diseases in delicate individuals. Pneumonia, for instance, or typhoid fever or chorea, and sometimes consumption or rheumatism, may be followed by a period of maniacal excitement. Severe injury to the brain or the pressure due to the presence of a brain tumour, may also be a cause of mania. A certain number of good authorities in mental diseases have called attention to the fact that mania is a little more liable to occur in patients who are suffering from heart disease. By this is meant in persons who have some organic lesion of the valvular mechanism of the heart. This leads to disturbance of the circulation and interferes with cerebral nutrition, thus predisposing to functional brain disturbance.
While melancholia occurs very frequently in older people, mania is almost essentially a mental disease of the young. The vast majority of cases occur between the twelfth and thirty-fifth year. The subjects of the disease are usually those who possess what is called the sanguine temperament, that is, hopeful, enthusiastic people, easily excited and aroused, easily cast down. Mania is much more common in females than in males.