The physical basis of personality / by V.H. Mottram.

  • Vernon Mottram
Date:
[1944]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The physical basis of personality / by V.H. Mottram. Source: Wellcome Collection.

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    All these generalisations seem to fit in with the biological, or rather the main biological function of woman, so there appears to be some justification for them. But justification or not, it hardly matters so long as there is a general agreement, which I think is undoubted, that sex conditions personality. Sex is, as we shall show, definitely determined by the nature of the chromo somes dealt out to the sex cells. The proof is almost as definite as it could be. Right through the animal kingdom the sex of the animal is determined by the chromosome make-up of the fertilised ovum. There may be variations, slight variations, in the exact plan followed, but so far as has been investigated—and this includes sea-urchins, nematode worms, grasshoppers, flies, moths, butterflies, beetles, bees, wasps, spiders, and mammals including man—it is thé chromosomes which determine sex. Above, the impression may have been gained, though warning notes were uttered, that the chromosomes are paired and alike, This is not quite true. Sometimes there is an unpaired chromo some. The rule that the body cells have an even number of chromosomes is true in some species only for the male and in others only for the female. One chromosome is missing. In the grasshopper, for instance, the male has 31 chromosomes and the female 32. And sometimes, though the total number of chromosomes is even, one of a pair of chromosomes is unlike its partner. It may be bent while the other one is straight, or it may be smaller than the other. This last is true of man. In the body cells of a man there is one chromosome markedly smaller than its partner; in woman the chromosomes which determine sex are alike. Before going further it will be best to see by diagram what must happen when sex cells are formed from cells having the normal complement of chromosomes, i.e. when reduction division takes place. We v could choose man to illustrate this, but the fruit fly is simpler because it has but few chromosomes altogether and the sex-determining chromosomes are markedly different. In the female there are two straight chromosomes and in the male one straight and one hooked (see Fig. 5). When the divisions which halve the number of chromosomes take place we have the result shown in Fig. 5, 2. The ova (a and h) all have identical make-up, but the sperm cells are of two types: one with a straight sex chromosome and one with a hooked chromosome (c and d, Fig. 5, 2). There are four possible