Bad heredity is by far the most common and important cause of arrests of development. There are, however, other factors acting during intra-uterine life or in infancy or early childhood which may cause them; two of these deserve special mention, parental alcoholism and parental syphilis.

Alcoholism in all its forms is encountered in the parents of idiots and imbeciles: chronic alcoholism, drunkenness at the moment of conception or during pregnancy, etc. Statistics compiled by Bourneville show that 48% of idiots and imbeciles are the offspring of alcoholic parents.

These figures correspond approximately to those published by most other authors. Yet the question of the effect of parental alcoholism upon the offspring cannot be said to have been fully answered. The fact that a large percentage of the parents of defective children are alcoholic lacks significance in view of the great general prevalence of alcoholism and in the absence of accurate data concerning the frequency of alcoholism in the parents of normal children. Further, there is much evidence which suggests that alcoholism is often but a symptom of neuropathic constitution, so that abnormal traits in the offspring of alcoholic parents may possibly be attributable to inheritance of the neuropathic taint rather than to the injurious effect of alcohol upon the germ plasm. Unfortunately statistics bearing upon this important subject have not always been very critically examined.

In a recent memoir from the Francis Galton Laboratory for National Eugenics, University of London,1 consisting in a statistical research of this subject, we find, among others, the following conclusions:

"There is a higher death rate among the offspring of alcoholic than among the offspring of sober parents.

"Owing to the greater fertility of alcoholic parents, the net family of the sober is hardly larger than the net family of the alcoholic.

"The general health of the children of alcoholic parents appears on the whole slightly better than that of the children of sober parents. There are fewer delicate children and in a most marked way cases of tuberculosis and epilepsy are less frequent than among the children of sober parents.

"Parental alcoholism is not the source of mental defect in offspring.

"The relationship, if any, between parental alcoholism and filial intelligence is so slight, that even its sign cannot be determined from the present material."

Inherited syphilis may act in two ways: either by giving rise to a congenital anomaly through intra-uterine disorders or by causing the appearance of meningeal and cerebral lesions during the first years of life of which arrest of development is the consequence.2

First Manifestations

According to Sollier, who has made an extensive study of these anomalies, the principal early manifestations are:

(a) Difficulty in taking the breast; it seems each time that the act is a new one to the child;

(6) Violent, continued, and unprovoked crying;

(c) Impossibility of fixing the child's gaze;

(d) Lack of expression in the physiognomy.

Later on, at the age when intelligence becomes manifest in normal children, the signs of psychic insufficiency become more and more evident. The child is sad, surly, or, on the contrary, extraordinarily noisy and turbulent. It does not speak or it may be able to say only a few words at an age when other children already dispose of quite a vocabulary. More important than the language of transmission is that of reception. The chief characteristic of the congenital imbecile is the restricted number of words, not which he can pronounce, but which he can understand.

1 Ethel M. Elderton and Karl Pearson. A First Study of the Influence of Parental Alcoholism on the Physique and Ability of the Offspring. London, 1910.

2 F. Plaut. The Wassermann Sero-Diagnosis of Syphilis in its Application to Psychiatry. (English translation by Jelliffe and Casa-major.) New York, 1911.

Physically arrest of development manifests itself most commonly in delayed walking and delayed acquisition of sphincter control. The so-called anatomical stigmata of degeneration are often seen, the most significant being the cranial deformities - microcephaly, macrocephaly, scaphocephaly, extreme brachy- or dolichocephaly.


As with the growth of the child the psychic functions become of greater importance, their insufficiency becomes more apparent and manifests itself in the impossibility of the subject's deriving the usual benefit from education. There is delay in learning to talk and later unusual difficulty and slowness in learning to read and write.

School age is eventually outgrown with but poor educational achievement, if any, and the patient, now almost grown up, is apt to begin to show all sorts of social maladjustments: sex immorality, vagrancy, criminal tendency, dependency, etc.

The mental defect varies in degree in different cases, and these variations constitute the basis of the generally adopted classification into four principal groups: (1) Idiocy. (2) Imbecility. (3) Moronism or Feeble-Mindedness. (4) Borderline Conditions.

These groups may be variously defined. In cases of adults a degree of general intelligence corresponding to that of an average child not over three years of age, as determined by mental measurement, characterizes idiocy; between three and seven years, imbecility; between seven and eleven years, moronism; and between eleven and twelve years, borderline conditions.

In many respects it is preferable to use as a measure the "intelligence quotient" (often expressed by the symbol IQ) instead of the mental age.1 According to this measure degrees of intelligence, both normal and abnormal, have been classified as follows: 2

Table 13

Above 140..

" Near " genius or genius.


Very superior intelligence.


Superior intelligence


Normal, or average, intelligence.

80- 90

Dullness, rarely classifiable as feeble-minded-ness.

70- 80

Borderline deficiency, sometimes classifiable as dullness, often as feeble-mindedness.





Below 20......


Very practical definitions, from a sociological standpoint, have been formulated by the British Royal Commission on the Care and Control of the Feeble-Minded: