Theories and facts as to palaeogenesis in its probable influence on the coloration of animals / by Jonathan Hutchinson.

  • Hutchinson, Jonathan, Sir, 1828-1913.
Date:
1912
Catalogue details

Licence: In copyright

Credit: Theories and facts as to palaeogenesis in its probable influence on the coloration of animals / by Jonathan Hutchinson. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    an important illustration of the fact that there is generally in the pregnant state a tendency to increase of pigmentation ; a sort of physiological or temporary Addisonism. Under its influences the well-known freckles, 11 chloasma uterinum,” are seen on the face. Such conditions are not peculiar to women, as is well- shown in several published portraits. Nor in women are they peculiar to the pregnant state. They are evidences of excessive general pigmentation with localisation by special causes. As regards the linea fusca, it is simply the abdominal streak common to most animals made conspicuous by pigmentation. In the male sex it is often not only pigmented but grows hair. A band of hair may be seen uniting the pubic patch with another patch very frequent on the mid-chest. On the chest the patch is often widened out, and being no longer a mere streak, clearly represents the abdominal mane of certain animals. In the human subject the dorsal streak so common and con- spicuous in animals is seldom well-marked. We are told that it is evident in Japanese children in the earliest months of life, and we recognise it more or less definitely in many adult males. It is seen especially in those of dark complexions and of the Semitic family. With it goes the mane in animals, and not very infrequently a growth of hair over the lumbo-sacral region. I have been accus- tomed to call the growth of hair in this region “ the porcupine- patch,” since it is the part upon which the porcupine develops its quills. Many white dogs develop a patch of dark hair in this region. It is reported that in woolly sheep, removed from tem- perate to tropical climates, the wool may, in the course of a few generations, be to a large extent dwarfed on other parts, but is retained on this and “looks like a dirty doormat across the animal’s rump.” Virchow, who observed it in the human subject, attributed it to defects in the spinal column, the so-called spina bifida occulta, but my explanation is, I think, the more probable. It is simply the remains, palaeogenetically, of the “ porcupine- patch.”