154 HEREDITY AND EUGENICS 



rules in certain families, as is known to be the case 

 with other Mendelian characters. For example, if 

 a defect has arisen in an ordinary chromosome, it will 

 be inherited probably according to the simple scheme 

 of a Mendelian dominant or recessive, but if it has 

 arisen in a sex chromosome it will be sex-linked. 



We have already seen that feeblemindedness is 

 essentially a condition of arrested mental develop- 

 ment. Epilepsy is a closely related neuropathic con- 

 dition. Insanity is more variable in its causes, and 

 is not always inheritable. Many data on the inheri- 

 tance of mental defects are given by Guyer (191 6). 



The relations between feeblemindedness and in- 

 sanity have frequently been misunderstood. From 



^ ^'xD "S^D 5^0 i)"^ D 



H A' . r-l A^ A.3 rJ^4 ^^r^6^7 16 ±9 1,0 ^,/ 





m |-h/ X2 X3 



Fig. 29. — Hereditary Imbecility in the Female Line. 



the point of view of the Binet-Simon tests, while 

 feeblemindedness gives general arrested development 

 at a certain level, insanity and epilepsy show '' scat- 

 tering " in the tests — i.e., in the diseased brain some 

 questions in various years will be missed. '' Scat- 

 tering " in tests of the feebleminded indicates the 

 oncoming of insanity, w^hich may not become evident 

 for several years. In many respects feeblemindedness 

 and insanity are at opposite ends of the mental scale, 

 although an unusually high percentage of feeble- 

 minded become insane. Psychiatrists maintain that 

 insanity comes in highly developed nervous systems, 

 which are easily thrown into an abnormal condition. 

 Morons, on the other hand, represent often a vigorous 



