230 A STUDY OF HEREDITY IN INSANITY [Oct. 



are, so to speak, of a more pronounced degree of recessiveness. 

 It appears in a most marked way that recoverable psychoses arc 

 dominant over epilepsy and allied conditions. 



It seems necessary to assume that the normal development and 

 function of the nervous system is dependent not upon a single 

 unit determiner in the germ plasm, but upon a group of deter- 

 miners, and that the number of units lacking from that group 

 determines the special type of defect to be observed clinically. It 

 may be recalled that a similar assumption has been found neces- 

 sary for the understanding of the inheritance of other Mendelian 

 characters, notably various shades of skin pigmentation." 



For convenience in presentation conditions of slighter degree 

 of recessiveness, like recoverable psychoses, may be designated 

 by the capital letter R, and those of more pronounced degree of 

 recessiveness, like epilepsy, by the small letter r. 



In Chart I " we find an instance of the union of a manic-de- 

 pressive subject, of a family heavily tainted with manic-depressive 



CHART I. L. R, CASE NO. 4215. 



(£) (^ 7* [1] [t] Cl] 



1. Insane before death. 



2. " Nervous prostration," in sanitarium four weeks, recovered. -^ 



3. Manic-depressive insanity, in State hospital. 



4. Manic-depressive insanity, in State hospital. 



5. Manic-depressive insanity, in State hospital. 



6. Epilepsy, in State hospital. 



7. Manic-depressive insanity, in State hospital. 



insanity, with a mate who is normal but who carries the taint of 

 epilepsy. That mating may be represented by the following 

 formula : 



RRxDrooDR + Rr. 



^'' Davenport. Heredity of Skin Pigment in Man. The American 

 Naturalist, Vol. XLIV, Nov. and Dec, 1910. 



" In all charts the following symbols have been employed : a square 

 indicates a male subject; a circle indicates a female subject; □ or O = 

 normal subject with normal progeny; or @ = normal subject without 

 progeny; M or ^ = normal subject with neuropathic progeny; ■ or • = 

 neuropathic subject; S or ® = subject died in childhood; [3 or (D^=data 

 unascertained. The type of mating is in each instance indicated by a small 

 letter: a, b, bi, c, d, di, e, as in Table II. 



