470 INTEMPERANCE AND INSANITY 



hereditary taint, although, as in other cases of reversion, it may 

 from time to time appear as a ' sport,' that is to say, without any 

 history of parental taint." x 



770. In other words imbecility is both a reversion and a 

 mutation. " A little thought renders it evident that the feeble- 

 minded person is always one with a defective memory. ... In 

 effect and in fact the feeble-minded person is an instance of 

 reversion to a pre-human mental state. But the reversion is not 

 complete ; for while he loses some part of his power of profiting 

 by experience, he regains no part of the lost power of being guided 

 by instinct. Therefore he is correspondingly helpless as compared 

 with a lower animal. The instincts (e.g. sexual) which normal 

 human beings still possess often appear unduly prominent in him, 

 but only because he cannot learn to control them." 2 



771. But if imbecility is a mutation, the reproduction should 

 tend to be Mendelian. It should be patent or latent in descendants. 

 It " is a sharp contrast to normality. Here, then, apparently we 

 have an explanation of the well-known fact that while the children 

 of a defective may all be normal, yet amongst the descendants 

 may appear individuals who are defective." 3 The Royal Commission 

 states in its Report, " In this connection the probable nature of the 

 swamping is of some importance. Speaking generally, the trend of 

 the evidence indicates that the offspring of feeble-minded persons are 

 either apparently normal or distinctly feeble-minded. In the same 

 family occur both types, the same person may have both normal 

 and feeble-minded offspring and descendants ; the defect may 

 skip one or more generations and appear later. It would appear, 

 therefore, that the swamping may be due not so much to a gradual 

 obliteration of the defect by a blending with normality, as to its 

 becoming latent or overlaid by the latter. It would seem also 

 that the probability of its re-appearance amongst descendants is in 

 some degree proportionate to the frequency with which it has 

 occurred amongst ancestors." 4 It seems, then, that the inheritance 

 of imbecility is comparable to that of such a trait as eye-colour. 

 We saw that black eye-colour is strongly dominant over one of a 

 lighter shade, but that after two or more infusions of the latter 

 (that is, after the lighter shade is derived in a patent or latent 



1 Op. cit., Appendices, vol. v. p. 247. 



2 Op. cit., Note on the Hereditary Transmission of Mental Deficiency, by G. 

 Archdall Reid, Appendices, vol. v. p. 247. 



3 Note on the Hereditary Transmission of Mental Deficiency, by G Archdall 

 Reid, vol. v. p. 248. 



4 Op. cit., vol. viii. p. 184. 



