MENTAL DEFICIENCY

Evening Post, Volume CVI, Issue 55, 13 September 1928, Page 6

MENTAL DEFICIENCY

HEREDITY AND DISEASE CLOUDS OF MISCONCEPTION A DEAD DOCTRINE (By P. Fraser, M.P.) IV. How far do tho facts and theories, sometimes the conflicting theories, of biology throw light upon the question of the inheritaucfi of mental deficiency and other weaku*,s«es in man? Professor H. S. Jennings, of the John Hopkins University, goes so far as to say that the habit of conceiving "heredity" as something in itself, an entity, a "force," something that itsolf does things, has induced clouds of misconception. He says that possibly we would be better off without * any such concept as heredity. When the length to 'which pseudo-scientists, particularly the popularisers of eugenics, have gone in their exploitation of the whole subject, is understood, there must be general agreement with Jennings. Amidst a mass of fluctuating uncertainty and uncertainties, for even the long accepted theory of tho noninheritance of acquired characteristics, is challenged, the cheap-jack type of cugenist, .with his loudly advertised universal -panacea of sterilisation, alone speaks with assurance based not upon JmAvvledge and proved fact, but upon conjecture, assumption, and supposition. This kind of eugenist usually speaks not with the authority, of science, but with the audacity of sheer charlatanism. A passage from Professor Jennings's brilliant little book, "Prometheus or Biology and the Advancement of Man," is well worth quoting to illustrate how impossible) it is to lay down any hard and fast rules in regard to the inheritance of characteristics in man: This doctrine of the all-might of inheritance is still proclaimed by tho popularisers of biological science. But this theory of representative particles is gone, clean gone. > Advance in the knowledge of genetics has demonstrated its falsity. Its prevalence was an illustration of the adage that a little knowledge is a dangerous- thing. Tho doctrine is dead—though as yet, like the decapitated turtlo, it is not sensible of it. It is not true that particular characteristics are in any sense represented or condensed or contained in particular unit genes. Neither ore-colour, nor tallness, nor feeblemindedness, nor any other characteristic, ia a unit character in any such sense. There is, indeed, no such thing as a "unit character," and it would be a step in advance if that expression should disappear. I have already quoted Professor T. H. Morgan as stating that it is extravagant to claim that there is a singlo Mendelian factor for feeblemindedness, and feeble-mindedness, ac cording to Professor Punnett, of Cambridge, is the most thoroughly investigated characteristic in man. Mr. J. B. S. Haldane, M.D., f.E.S., Header in Biochemistry, Cambridge University, who has had very considerable first-hand knowledge of animal and plant breeding, and who has helped substantially to advance knowledge concerning heredity, after explaining some facts about proved characteristics which are inherited, and which were included in the list already given in our second article, writes:— The inheritance of other desirable and undesirable characters is far less clearly understood. Feeble-minded ness is fairly strongly inherited, but unfortunately it is generally inherited in such a way that the segregation or massacro of tho feebleminded, even if continued for several generations, would not stamp it out. The feeble-minded, unless they mate with one another, do not necessarily produce feeble-minded children. If, therefore, the feebleminded are to be segregated, it should be in their own interests, and because thoy are unfit to bring up a family, quite as much as on eugenic grounds. Professor J. Arthur Thompson, of Aberdeen University, Who is always scientific and careful in his conclusions, writing on the subject of '' Heredity and Disease," says:— In regard to this very difficult question we wish simply to make throe remarks: (1) In many cases what the facts suggest is the inheritance of a general, not a specific, predisposition; (2) on the other hand, there are some instances of apparently very precise and specific inheritance, as if some very definite "blot on the brain" was transmitted from ■ generation to generation; and (3) that there seems to be little warrant for believing in the transmission of a nervous disorder of exogenous origin. Professor Thompson continues:— In most cases the facts seem to suggest that what is inherited and transmitted is a general predisposition to somo dislocation or derangement of the nervous system. If such a dislocation or derangement occur in a case where we can exclude tho probability of its being due to any infection, intoxication, or lesion of external origin, we must refer it to some initial defect or disturbance in the organisation of the germ. As such, it is likely enough to be transmitted, whether it be hysteria or epilepsy, melancholia or idiocy; but it does not by any means follow that it must be transmitted, or that, if transmitted, it will have in tho offspring the form it took in the parent. In fact, the frequency with which the expresses change almost forces us to conclude that what is inherited is something general, not specific. He further says:— On the other hand, there arc some cases —a small minority-—which suggest that a specific predisposition may be inherited. Professor F. W. Mott says:— It is not necessarily insanity that is inherited, but a nouropathic tendency iv tho stock which manifests itself in many forms, e.g., epilepsy, asthma, migraine, chorea, diabeteß. exophthalmic goitre, neurasthenia, eccentricity, hysteria, criminality, fanaticism, suicide, genius of a certain type, and insanity. Professor Thompson quotes Dr. T. S. Clouston as saying:— A neurotic heredity is seen to resolve itself into general morbid ten"dencies rather than direct proclivities to special diseases. Professor Thompson states what seems an evident fact in the following passage: Tho chromosomes of an individual usually represent eight families, and it is therefore likely that everyone has some chromosomes with a predisposition <o some Jisease, sich as phthsis, or gout, or diabetes, or "nerves." A mosaic made up from contributions from eight families can hardly avoid such taint. In discussing "Anticipation and In-

tensificatiori in -Disease," Professor Thompson gives it as his opinion that: In tho present state of our knowledge it is impossible to be otherwise than vague in regard to theso things. In regard to constitutional diseaso hu writes: — It seems to us that even expert writers have sometimes exaggerated tho necessity of the persistence of constitutional taints and defects; for as it is well known that a highly advantageous variation may fail to persist, why may this not be equally true- of one that is highly disadvantageous?" Thompson further states:— If wo accept the chromosome theory we can readily understand how an. innate defect or morbid predisposition in, let us say, a grandfpther, may be sifted out of the lineage, and similarly for a virtue. It is well to make it plain that both Professor Thompson and Professor Jennings express disapproval of the freedom and encouragement of reproduction among tho feeble-minded and tho insane. As might be expected, and as we shall see in our next article, from their knowledge of the immensity, tho complexities, the difficulties of the problems involved, biologists generally are very careful not to be too sweeping or rash in applying biological theories to mankind, and we find them generally unconvinced as to the advisability of such "eugenic" proposals as sterilisation. Indeed most of them strike a warning note in regard to such methods. It would appear that most biologists are opposed to such proposals as sterilisation on tho ground of the scantiness of proved fact in regard to heredity.