by injurious external factors acting alone, and that in an overwhelming proportion of cases the cause lies in the condition of the germ plasm." 10 He attributes about 80 per cent to heredity.

It seems clear that the feeble-minded taken as a whole include cases of various sorts, due, very possibly, to widely different causes. About one-half of the idiots appear in normal families in which we find no history of other defectives. One distinct type marked by features which has led to their being called Mongolians appear in many ways like the runts in litters of pigs. Often they come from families otherwise normal. They seem to be cases of arrested development, as if nature could not finish its task. They are very uniform as to mental age (seven) and die on the average at fourteen, seldom reaching the age of thirty, though Tredgold reports one who lived to be fifty-seven. The age at death of all the feeble-minded is low, though the life span seems to increase in institutions. In 2,801 cases in our institutions the age at death was 20.3 for idiots; 22.9 for imbeciles and 28.5 for morons. The crude death rate in England is about 20 but in institutions for aments it is over 30. Some of the feeble-minded appear to lack certain of the internal glands, a condition which may be hereditary. Tredgold 11 states that the thymus gland was lacking in 74 per cent of 292 cases examined. Years ago David Starr Jordan described the cretins of Europe and showed how the condition had been remedied by doses of thyroid glands.

Granted the rôle of disease or accident in many cases, as Tredgold says: "A close examination of the brothers and sisters of the affected individual will usually reveal some indications of mental abnormality." 12 He cites an investigation by N. E. Sayer which compared the family history of normal and defective children.

The discovery in the school at Vineland, New Jersey, of related children led to a very complete investigation of the

family history of the inmates which revealed an altogether unsuspected amount of feeble-mindedness and gave a great impetus to similar studies elsewhere.

A study of the three following charts will help make clear the situation. The cases are chosen practically at random.

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1

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FIG. 24. THE INHERITANCE OF FEEBLE-MINDEDNESS 14

In the first we have the intermarriage of related lines which carry the common characteristics of illegitimacy, incest, high infantile death rate and a large percentage of feeble-minded

In the second we see again the results of the marriage of two affected individuals and also the effects of crossing a normal stock with an affected stock even though the member of the latter be normal. In the third we have another illustration wherein the father of normal descent had normal

children only by his first wife; while a later marriage with a feeble-minded woman produced at least three feeble-minded children.

When one studies such charts he can hardly fail to conclude that the feeble-minded represent, in great part at least, a defective strain of mankind which may reproduce itself under favorable conditions just as does any race of animals. It is admitted that it is difficult to get accurate information about most individuals of earlier generations and that overzealous investigators may have exaggerated at times. Yet the fact that, in so far as we know, two feeble-minded parents never have normal children lends much weight to other

First Marriage

Father Remarries

11 children all normal

Three children defective

FIG. 26. CONTRAST IN CHILDREN OF TWO MARRIAGES

evidence. Goddard has cited an apparent exception to the last statement wherein two normal children appeared in a family where the reputed parents were feeble-minded and the rest of the children were also but the normal children were mulattoes while the alleged father was white. It is not unlikely that other seeming exceptions in feeble-minded families would be explained if we knew all the facts.

That which must be emphasized is that the feeble-minded are not backward normal children. They may learn a good deal; they may have rather marked sensory development as of sight or smell or sense of rhythm. but by no training can they be made normal. The lower idiots and imbeciles rarely can or do become parents. The morons may and do have children both in and out of wedlock. Thus the threat to the race stock does not come from the lower groups but from the upper. This danger is enhanced by the fact already noted that the condition often acts as a recessive and may appear therefore though the parents be normal themselves. It should be noted that the feeble-minded often become insane in later years.

FIG. 27. NEUROTIC INHERITANCE 16

Affected individuals shaded. I, insane; E, epileptic; +, dead, facts unknown.

Insanity

There are many forms of insanity and the word should be used in the plural perhaps rather than in the singular. The causes of some of these forms are known and it is sometimes said that 50 per cent of the cases could be prevented while not more than 25 per cent can be cured. Syphilis, alcohol, and worry are generally stated to be the three great causes. No brain or nervous system can stand up if attacked by syphilis so far as known. But it is not so easy to explain why alcohol and worry drive some insane and not others. It may be that there are human types, to be called neurotic, which are almost certain to break down if to the ordinary vicissitudes of