TRANSMISSION OF CHARACTERISTICS 95 



or body, maladies are liable to skip one or more 

 generations. Haller noticed the recurrence of idiocy 

 in a noble family in the fourth or fifth generation 

 after its first appearance. It is also apt to appear 

 collaterally, an uncle or an aunt of a particular patient 

 being frequently affected. This would seem to show 

 that the germ of the malady existed in a previous 

 generation, although its presence may not have been 

 suspected. It is highly improbable indeed that an 

 idiot should be born of perfectly sound parents. 

 Of the heredity of idiocy medical literature furnishes 

 abundant proof. Insanity, which is a derange- 

 ment of the functions of a brain more or less per- 

 fect in appearance, is similar in its manifestations, 

 except that the patient may have lucid intervals, or 

 even appear to be cured. It may follow the direct 

 line of descent, or may appear collaterally. The 

 fact that insanity, unlike idiocy, may exist without 

 any perceptible deterioration of the brain tissue has 

 led some to doubt whether it was invariably connected 

 with physical causes, but the argument that no physi- 

 cal cause exists because none happens to be visible does 

 not hold water. Our knowledge of matter is bounded 

 by the powers of the microscope. Every increase 

 made in our magnifying apparatus reveals the exist- 



