Mental Deficiency (Amentia)
- Author:
Tredgold, M.D., F.R.C.P.,
F.R.S.E. 6th Edition. Bailliere, Tindall and Cox. 25/-.
To all who are interested in the welfare of the mentally defective, the appearance of a new edition of Dr. Tredgold’s ‘Amentia’ is something of an event. Indispensable alike to the student and to the specialist, for almost thirty years this work has served as an authoritative guide to the study of mental deficiency, and being founded on the author’s own unrivalled experience, it conveys a vivid impression of a personal study written with a grace of phraseology and a precision of thought seldom encountered in medical literature.
As indicated in the preface, the new edition, which is larger than its predecessors by twenty-two pages, has been extensively revised; the chapters on Aetiology, Psychology, Pathology, Secondary Amentia and Sociology have been almost entirely re-written; those devoted to the Nature of Mental Defect, Clinical Examination, Mental Tests, Diagnosis and Legal Procedure have undergone considerable amplification, and a section has been added on the Chronological Development of the Normal Mind.
In his discussion of Aetiology, the author recognises four groups: (i) Amentia due to inheritance, (ii) Amentia due to environment, (iii) Amentia due to both these causes, and (iv) Amentia without discoverable cause. For the first group, Dr Tredgold claims a preponderating influeuce, in his opinion, no less than eighty per cent, of all defect being attributable to inheritance?some germinal tendency or peculiarity. Since importance is attached to the influence of a ” neuropathic diathesis ” in the germinal basis of mental defect, it is of some interest to note in this connection that a recent investigation conducted by a special committee of the Royal MedicoPsychological Association revealed the presence of a similar vitiation in the antecedents of more than fifty per cent, of apparently normal persons; a finding of this sort suggests that in elucidating the causes of mental defect it is perhaps possible to attach too much importance to a family history of ” neuropathic diathesis Cases of amentia due entirely to environment are considered to comprise about twenty per cent, of defectives of all ages, though Dr Tredgold recognises that since a large number die in the early years or months of life, the proportion of secondary cases is probably higher than this.
The number of cases of amentia without discoverable cause is put at not more than one or two per cent, of all aments, a percentage which by many will be regarded as an unduly optimistic index of the present state of our knowledge of the causes of amentia.
Though Dr Tredgold places Mongolism in the category of primary amentia, and assesses its incidence at about five per cent, of the total number of aments of all ages, he is forced to admit that its causation is still largely a matter of conjecture. Would it not be more prudent, then, to place this distinctive type in the category “amentia without discoverable cause” ? In the chapter devoted to pathology the view is retained that mental deficiency has, as its material basis, an inadequate development or persistent imperfection of function of the neurones of the mantle of the brain, but a note of caution is now introduced in as much as the author makes it clear that the histological changes described are those of low grade amentia. Since the neuropathology of high grade amentia is still an uncharted field, it is well that this point should receive recognition.
It may be questioned whether the advantage of simplicity which is possessed by Dr Tredgold’s method of recording cranial measurements, is not outweighed by its failure to yield data which can be compared with those obtained by the more orthodox methods of the anthropologist. As the breadthlength ratio or cephalic index of the skull affords a very useful and concise way of recording certain anomalies of the cranial vault, and requires for its determination only a simple form of head calliper, it is to be regretted that the author does not recommend its use in clinical work.
In the description of secondary amentia, the clinical varieties are now grouped under the headings, traumatic, infective, degenerative and deprivative. This is a new and admirable form of classification which should prove extremely useful.
One curious omission must be noted. Though the book has been brought up to date by the inclusion of certain rare forms of amentia which have only recently been described, of which Gargoylism and the amentia associated with Phenylketonuria are examples, no reference is made to the LaurenceMoon-Biedl syndrome, which has as its cardinal features, mental retardation, obesity, hypogenitalism, Polydactyly and retinal pigmentation. This is somewhat surprising as the condition has been known for more than sixty years, and with one or two exceptions, all its victims have shown varying degrees of mental defect.
The maze of complexities which underlie the behaviour problems of the moral defective are discussed very fully in a chapter of sixty pages, and this must be reckoned as one of the most valuable sections of the book. It is safe to depict that the s;xth edition of ” Mental Deficiency ” will maintain its place as an outstanding and comprehensive contribution to the study of amentia. R.M.S.
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