A472 SECTIONAL TRANSACTIONS.—4J. 
Division 2. 
Dr. BE. O. Luewts.—The Social Aspects of Mental Deficiency. 
The significance of the social problem which mental deficiency presents cannot 
be appreciated unless we have a clear conception of the nature of this abnormal 
condition. Whether we approach the subject from a biological, etiological, clinical 
or social standpoint, mental deficiency comprises a complexity of conditions. Its 
composite character is recognised in some of the generally accepted classifications of 
defectives such as those into primary and secondary cases of amentia, familial and 
non-familial, inherited and sporadic cases. Each of these classifications has its 
apecial merits, but in a discussion of the social aspects of the problem the simpler 
classification into the pathological and the sub-cultural types seems more helpful. 
The pathological cases are those in which there is a definite organic lesion or 
abnormality—cerebral hemorrhage, hydrocephalus, euchorine deficiency, or some 
physical defect due to toxic factors that have impeded growth during childhood or 
at the foetal stage, or may have impaired the germ-plasm of one or both parents. The 
sub-cultural type of defective is merely a variant of the normal. Intelligence is 
distributed in accordance with the normal curve of distribution and the sub-cultural 
group of defectives are represented by the lowest part of thiscurve. The pathological 
deficiency is a definitely abnormal condition, whereas sub-culiural type is merely a 
normal variation. 
In a discussion of the social aspects of mental deficiency the sub-cultural group 
is all important, whereas the pathological group has comparatively little significance. 
The pathological group includes considerably less than half of the mentally defective ; 
its members are mostly low-grade and need little more than custodial care and some 
simple form of training, and they are fairly evenly distributed amongst the various 
social grades of the community. The sub-cultural defectives, on the other hand, are 
much more numerous—not infrequently several are found in the same family. A 
large proportion of these families form an important group in the lowest social strata 
of the population, and give rise to many of the chronic social problems of our nation. 
The higher the species in the biological scale the greater is the variety of form, 
function and behaviour amongst its individual members. Mental deficiency of the 
sub-cultural type may be regarded as one manifestation of this variety. This 
variation in the endowment of innate mental characteristics seems to increase, or at 
least to become more conspicuous as civilisation progresses. The complexity of 
industrial and social conditions prevailing in a civilised community, especially if the 
economic system has a competitive basis, makes manifest the wide variations in 
-mental and physical capacities of the individuals comprising the community. 
Viewed from this standpoint the problem of the sub-cultural group of the mentally 
defective can be said to be an inevitable concomitant of a progressive civilisation. 
These variations amongst the population, especially if of sub-normal character, 
add considerably to the difficulty of maintaining the cohesiveness of the social group. 
Certain economic and social factors tend to produce a social system in which the 
sub-normal members are segregated in certain districts; and the economic and 
social failure of large numbers of the men and women who belong to this group results — 
in their becoming a financial burden upon their families or upon public funds. The 
assimilation of this sub-cultural group and of the still larger contiguous group—the 
sub-normal tenth—into the general life of the community, constitutes one of the 
most difficult problems that western civilisation has to solve. The process of finding 
a solution will probably evolve new conceptions of the social hierarchy and of the 
mutual obligations of the various groups in the general community. 
Prof. F. A. E. Crew.—The Genetic Background of Mental Defect. 
The geneticist is not responsible for the description of characters, the mode of 
inheritance of which he studies. He accepts the descriptions and definitions of 
others and concerns himself solely with the interpretation of the facts relating to the 
distribution of characters among successive generations. In the case of the human 
subject the geneticist does not even collect his own data ; his materials are the records 
of the clinician. The pedigrees he examines have all too commonly been constructed 
by such as are unskilled in psychology or else in genetics, and who accept anecdote 
in place of evidence. It is not surprising, therefore, that amongst pedigrees examined 
mental defect in different cases demands, in explanation of its distribution, the action 
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