THE INHERITANCE OF DISEASE 5O7 



almost infinite variety and the study of them has gradually 

 become a very intricate specialty. From our present point 

 of view only certain outstanding selections can be considered 

 for purposes of illustration. 



Feeblemindedness has a peculiar interest. The condition 

 (one, it may be supposed, of Hmited development) rests in 

 some instances on an inherited basis as made evident by 

 careful and competent scientific investigation. Is feeble- 

 mindedness a disease? Obviously it may be so regarded in 

 the social sense, since on a purely practical basis a highly 

 developed society is forced to maintain large institutions for 

 the care of such of its offspring as are unable to maintain the 

 pace. From the pathological standpoint it is hardly to be 

 looked upon as a disease except in the most extreme or 

 particular instances. But when one begins to discriminate 

 on a quantitative basis all the standards must be arbitrarily 

 chosen. The question clearly becomes an academic one 

 when purely practical standards are disregarded. The same 

 may be said of many types of insanity. The discrimination 

 between sane and insane in ^neral is possible on a legalistic 

 and practical basis, however difficult decision in particular 

 cases may be. A perfectly sharp borderline in the scientific 

 sense can hardly be drawn. 



But insanity presents another aspect, in that there are 

 certain disorders of the nervous system characterized by 

 definite symptomatic behavior which clearly define them 

 without reference to their severity or, in other words, 

 whether the sufferer is incapacitated or not. The most widely 

 illustrative perhaps is the disease known as essential epilepsy. 

 Those most slightly affected may not only be not incapaci- 

 tated but may be mentally quite normal or unusually 

 brilliant people. Those most severely affected are or fre- 

 quently become unquestionably insane. In its mildest forms 

 or in its most severe, the symtomatology is characteristic. 

 The difficulties of recognition in the mild cases are due to 

 the fact that the slight symptoms long pass unnoticed. This 

 disease is inherited in many cases, and apparently usually 

 as a Mendelian recessive. There are indications of sex 

 linkage in some instances and it sometimes appears as a 

 dominant. Multiple factors are probably involved. Other 



