The incidental or contributing causes are remarkable for their multiplicity and complexity; one might almost say that they are as many as there are individual cases and that in no two cases is their manner of action exactly alike. In themselves, however, they do not suffice to produce a mental disorder, but acquire pathogenicity only in the presence of an essential cause.

Some are met with in practice with special frequency and therefore seem to possess quasi-specific potency in the production of mental disorders.

Alcoholism, which has been already mentioned as an essential cause, may also act as a contributing cause in the presence of a predisposition created by one of the other essential causes. Thus, acting on a basis of bad heredity, alcoholism may determine the development of dementia praecox or of a manic-depressive or an epileptic attack; and some hold that a syphilitic subject who is also intemperate is move likely to develop general paralysis than one who is abstinent. Thus, of the 16.2% of first admissions to the New York state hospitals during the year ending June 30, 1918, in which there was a record of intemperance, only 5.2% were cases of specifically alcoholic psychoses, the remaining 11.0% being cases in which alcoholism played the part merely of a contributing cause.1

1 Thirtieth Annual Report of the State Hospital Commission, Albany, N. Y., 1919.

Head injuries, like alcoholism, are probably capable of acting not only as essential but also as contributing causes, especially as factors in the etiology of general paralysis; their importance in this connection will be again discussed in the chapter devoted to this disease.

For the rest, recent studies seem to indicate that the incidental or contributing causes that are met with are psychic rather than physical in their nature or manner of operation.2

Even such causes as pregnancy, abortion, rhildbirth, and lactation are found in the better analyzed cases to act not as physical causes, but through psychic accompaniments, such as illegitimacy, increasingly hopeless domestic infelicity, apprehension of added hardships; although it is undoubtedly also true that such conditions as febrile or exhaustion deliria may be produced by these causes acting in a physical way, especially in the presence of complications like excessive hemorrhage or infection.

Among the plainly psychic causes may be mentioned the following as being the more common: Business troubles: financial difficulties, loss of employment, inability to get employment, failure in school examinations. Domestic troubles: abuse by husband, infidelity of husband, intemperance of husband, desertion, other conditions of marital infelicity. Love affairs: disappointment in love, unrequited love. Death or illness of relatives.

1 Thirtieth Annual Report of the N. Y. State Hospital Commission Albany, 1919.

2 Adolf Meyer. The Role of the Mental Factors in Psychiatry. N. Y. State Hosp. Bulletin, N. S., Vol. I, 1908, p. 262. - Jung. The Psychology of Dementia Pra?cox. English translation by Peterson and Brill, New York, 1909. - A. J. Rosanoff. Exciting Causes in Psychiatry. Amer. Journ. of Insanity, Vol. LXIX, 1912, p. 351. - August Hoch. Precipitating Mental Causes in Dementia Praecox. Amer. Journ. of Insanity, Vol. LXX, 1914, p. 637.

The relative parts played by the essential and incidental or contributing causes are not the same in all cases.

In such conditions as arrests of development, epilepsy, marked constitutional psychopathic states, and Huntington's chorea bad heredity alone suffices to produce the infirmity and to render it manifest.

In the constitutional psychoses, too, the factor of bad heredity seems often to be the all important one. " In more than half of the cases indications for commitment have arisen in the midst of an average environment and in the absence of occasion of special difficulty or strain." 1 " On the whole exogenous factors appear to be of but minor importance: the amount of psychotic manifestation is, for the most part, like its kind, predetermined in the germ plasm." 2 It is a remarkable fact, significant in this connection, that the World War produced no increase in the insanity rate, as judged by numbers of cases admitted to institutions.3

In the psychoneuroses environmental factors often determine the manifestations; i.e., while here, too, the disorder cannot arise in the absence of the constitutional factor, that factor alone, in a large proportion of the cases, produces no manifestations, but remains latent until some external cause brings it to light. This accounts for the vast numbers of psychoneuroses observed in all armies during the World War.

1 A. J. Rosanoff. Exciting Causes in Psychiatry. Amer. Journ. of Insanity, Oct., 1912.

2 A. J. Rosanoff. Dissimilar Heredity in Mental Disease. Amer. Journ. of Insanity, July, 1913.

3 Board of Control, Great Britain. Insanity and the War. Third Annual Report, 1916. - R. H. Steen. Fifty-first Annual Report. London Asylum and Hospital for Mental Diseases, 1916. - K. Birn-baum. Kriegsneurosen und -psychosen auf Grund der gegenwartigen Kriegsbeobachtungen; erste Zusammenstellung vom Kriegsbeginn bis Mitte Marz, 1915. Zeitschr. f. d. gesamte Neurologie u. Psychiatrie, 1915.