GROUP I. PSYCHOSES DUE TO IMPER FECT DEVELOPMENT OF THE BRAIN.
Idiocy and Imbecility. — These two conditions of defective mental function are merely different in degree. They are both dependent upon defective or ar rested cerebral development. This de fective development may be hereditary, congenital, or acquired; that is, it may occur in intrauterine life, during the parturient process or after birth. In the United States idiots and imbeciles are generally grouped under the term "feeble-minded." Idiots sometimes appear to be without any intellectual development whatever, having no power of thought, memory, or judgment. But these extreme degrees, if they occur at all, are rare. The sensory organs may be normal, and the vegetative functions well performed.
In imbecility the arrest or perverted development of the brain has not pro ceeded to the same degree, and there is more or less intellectual power. The memory and certain special faculties, as the musical, are sometimes highly de veloped in imbeciles.
Frequency.—The proportion of feeble minded is about 1 in 500 of population. Males outnumber females 2 to 1.
Causation.—Idiocy and imbecility are hereditary in about one-half of all cases. The principal conditions in the ancestry supposed to influence the heredity are insanity, nervous diseases, intemperance, consanguinity, and tuberculosis. Con trary to general belief, intemperance in the parents is a factor in only about 10 per cent.
In an area of four square miles in County Meath, Ireland, with a popula tion of about 300 persons, one-half of the families have one or more insane, sui cidal, idiotic, or goitrous members. At tributed to consanguinity and heredity, as the conditions under which the people live and their agricultural employment neither account for the endemic 110I' serve to limit it. Lallan (Brit. Med. Jour., Sept. 20, '00).
The causes of idiocy and imbecility are many and varied. Subtle causes, such as maternal impresSions during preg nancy, must not be accepted without searching for more substantial under lying causes. Hereditary degeneracy, psychoses, and psychoneuroses of the parents are some of the causes. Acute
infectious and contagious diseases of the mother during pregnancy are causes, but additional search must always be made for underlying causes other than these. Syphilis is a cause. Autoinfec thm, myxmdema. is a cause. If the acute contagious and infectious diseases during childhood leave the child an idiot or an imbecile, that child's hered ity must be well scrutinized, as the lat ter is most certainly the underlying cause. Alcoholism of the parents is the major cause responsible for the birth of idiot and imbecile children, according to the study of the cases cited. Alcoholism of the parents not only causes idiocy and imbecility of the offspring, but also acts as a strong factor in reducing the birth-rate and increasing the death-rate. Children of alcoholic parents, if not idiots or imbeciles, are apt to be invalid in many other ways. Children of alco holic parents generally die in early in fancy of meningitis. L. G. Robinovitch (Jour. of Mental Path., July. 1901).
A considerable proportion of cases of feeble-mindedness is doubtless due to traumatisms during the process of birth. Prolonged labor, subjecting the brain to undue compression, direct traumatisms from the use of instruments or improper methods of delivery; convulsions in the mother, with consequent poisoning of the fcetal blood by carbon dioxide or by anes thetics used to relieve the maternal con vulsions; or premature birth may pro duce such a disturbance of nutrition in the brain as to arrest or retard its de velopment. It is probable that the num ber of children in whom the arrest of de velopment has begun at the time of birth is much greater than is generally sup posed. Many of the cases of idiocy and imbecility among the offspring of parents entirely healthy, or of high intellectual ability, and which furnish such choice food for heartless gossip among the ignorant and uncharitable doubtless be gin as the result of some such avoidable or unavoidable accident. The actual pro portion is not ascertainable.