Pigmentation

“ The increased pigmentation at the umbilicus and in the median line is scarcely to be classified among the abdominal changes, as the skin elsewhere presents the same discolored appearance. The degree of pigmentation varies with the complexion of the individual, as blondes may be but slightly tinted while the discolored areas on a brunette may be dark brown, sometimes almost black. ”

“ Pigmentation is common; the face becomes dusky red, the rest of the body a dark brown shade. This darkening is most marked in situations normally pigmented and in parts exposed to pressure of the clothes, such as the neck, axilla, and inner aspect of the arms, the extensor aspects being less marked than the flexor. ”

“ In this way we have seven distinct grades of pigmentation, and the series is further complicated by the fact that these various grades exhibit a rather different amount of pigmentation according as they occur in a male or a female bird, for, generally speaking, the female of a given grade exhibits rather more pigment than the corresponding male. ”

“ The pigment cells can not be made to show themselves, even by a prolonged stay in the light. The old, if kept in the light, will not become darker, and a young one reared in the light until ten months old not only showed no increase in the pigmentation but lost the pigment it had at birth, taking on the exact pigmentless coloration of the adult. ”

“ While dark-haired people show pigmentation in a very marked manner, those with red hair show it slightly or not at all. In some peculiar manner red-­haired people appear to possess a comparative immunity to the effects of intestinal stasis. Except for the face, the areas that show pigmentation most conspicuously are those exposed to friction, such as the inner aspects of the upper parts of the thighs, with the adjacent opposing surfaces of the buttock, the spines and abdomen where the corset or dress presses, the axillary folds, the bend of the elbow, and the neck. ”

“ Secondly, there seems to be some correspondence between the degree of pigmentation and the acuteness of smell, as the following facts suggest:—
In macrosmatic animals, such as the dog, cat, fox, sheep, and rabbit, pigmentation extends over a larger space and is darker in tint than in man. 126In these animals also the mucus covering the olfactory area of the nose is itself pigmented.
We have seen that human albinos are anosmic, and the same is probably true of animal albinos. ”

“ From the uncertainty of our knowledge as to the immediate cause of eye and hair pigmentation one cannot but be faced with the alternative—either that little formal attention has been paid to the subject, or that the elements of investigation are uncertain and conflicting. ”

“ Pigmentation of the Iris.—In regard to the coloration of the eyes, a change often takes place at puberty which is the opposite to that already noted in regard to the hair: the eyes become more uniformly light; this happens in the majority of cases.
In the coloration of the eyes it is necessary to distinguish two factors, the uvea and the pigment.
The iris has a fundamental and uniform light colour (due to the uvea) which oscillates, according to the individual, between blue and greenish. ”

“ These findings are the more noteworthy by reason of their contrast to the usual deep pigmentation of the Indian eye. Some of our specimens throw light on this phenomenon, for we observe in them two changes: (1) The pigmentary layer of the retina is irregularly thinned and altered, and at some points its pigment can be seen migrating into the choroid; (2) the choroidal pigment itself is extensively altered in an irregular manner, being heaped up in some areas and thinned in others. ”

“ Pigmentation of the skin occurs in many conditions—-as in normal pregnancy, uterine fibroids, abdominal growths, certain cases of heart disease, exophthalmic goitre, &c., and after the prolonged use of certain drugs—-as arsenic and silver. ”

“ This pigmentation shows itself (1) over exposed parts, as face and hands; (2) wherever pigment appears normally, as in the axillae and round the nipples; (3) wherever pressure is applied, as round the waist ”

“ The pigmentations of women during the phases of genital life, menstruation, pregnancy, the menopause and the fact that eunuchs are usually fair and fat, while deep pigmentation in the white race is usually associated with sexual irritability, all make interesting studies in this subject. ”

“ These experiments bring us to the conclusion that, all other things being equal, the Negro will suffer more from the heat effects of the sun than the lighter-skinned races, and all of the work tends to show that the rays of greater refrangibility in the violet and ultraviolet portions of the spectrum are not the important factors, except in so far as they cause sunburn and subsequent excessive pigmentation. ”

“ Nothing can be made to develop beyond the segmentation stage.
Some experiments like those of Dorfmeister, Weismann, Eimer, Merrifield and Poulton show the direct results of changes in temperature, food and even the color of the surroundings; but these affect the character of the pigmentation in these normally highly pigmented forms, and we shall see, as we go higher in phylogeny, that pigmentation is one of the easiest characters to alter through environmental differences. ”

“ In extraneous pigmentation we have coloured substances either in a solid or fluid state, gaining entrance into the organism and accumulating in certain tissues. The channels of entrance are usually by the respiratory or the alimentary tract, also by the skin. ”

“ The regions affected were mostly of a dirty-brown color, but in patches of a bluish-gray. The disease began suddenly in the woman, but gradually in the man. Crocker has reported a case somewhat similar to these two, under the head of general bronzing without constitutional symptoms, in a Swedish sailor of twenty-two, with rapid onset of pigmentation. ”

“ The patches grow slowly, are milky or dead white, smooth, non-elevated, and of rounded outline; the bordering skin is darker than normal, showing increased pigmentation. Several contiguous spots may coalesce and form a large, irregularly-shaped patch. Hair growing on the involved skin may or may not be blanched. ”

“ Others, further advanced in development, are small, sessile, or pedunculated hard outgrowths, without bluish colour and sometimes covered by thickened epidermis. There is a large patch of pigmented (brown) skin on the dorsal surface of the right foot, and in the neighbourhood of this pigmented area are some minute nodules of similar character to those already described. It is possible that the pigmented skin has been the site of minute growths which have undergone spontaneous involution, and have, as frequently happens in Lichen planus, left pigmentation of the skin behind them. ”

“ The suggestion has been made that two gametes both having the determiner for yellow are incapable of uniting in fertilization or that they are not viable if they do unite. ↑ To mention even the chief of these papers, the most of which are based on data or methods inadequate for conclusive results, would require too much space. ↑ Anthropologists have devoted much attention to the highly complex problem of the difference in pigmentation between urban and the surrounding rural populations. Ripley in his "Races of Europe" gives a good general discussion, to disease. ”

“ Where the cuticle is thick, the color of the pigment will predominate over the other elements on account of the greater depth of pigment-cells. "Where it is thin, and the coloring matter light, the tint of the skin will be much affected by any change in the supply of blood to the capillaries at the surface of the body. This is the reason why the whites alone can turn pale and blush.
Closely related to the pigment of the skin are the coloring matters of the eye and hair. Dark-skinned people usually have black eyes and hair ”

“ Little specks of coloring matter, or pigment, which lie in the outer layer of the skin. Even white skins contain a little pigment, they are not a pure white. A Chinaman’s skin has a little more of this pigment, so that it looks yellow; an Indian’s has still more; and a negro’s has most of all, making him black.
Sunlight can increase the amount of pigment in the skin. The people who live in the torrid zone have much darker skins than those who live where the days are short and cold. ”

“ The skin rested, as did the brain, so that it seemed probable that central activity, thought, will, or whatever name is given, has some effect in the change of color. The probability is that, as they become pale, the pigment does not leave the skin, but that it is collected in spheres too small to affect our retina, which will be impressed by the same quantity of pigment when more extended. ”

“ The colouring of the hair depends not only on the pigment, but on the more or less quantity of air in the medulla of the hair, which blends the white and grey tones with the general tint given by the pigment. In the air, the hair fades, becomes less highly coloured, duller. Certain acids of the perspiration render the hair reddish-brown, as for instance, under the arm-pit.
At birth pigment is found in the body in less quantity than in the adult state. Every one knows that the hair of children, often light-coloured at birth and in early years, becomes darker as they grow up. ”

“ Yet from the very happy circumstance of the conspicuousness of the pigment, the results of their activity could be observed with the utmost facility, and their behaviour in relation to inflammatory congestion easily studied even under a low magnifying power.
The pigment cells pervade the skin and subcutaneous tissue of which the frog's web consists, and are especially numerous about the blood-vessels, round which their branches twine abundantly. They must, therefore, be acted on along with the vascular parietes by anything applied to the surface of the membrane. ”

“ Some people are born with these pigment spots; but when the freckles come out from long exposure to the sunlight, they are an example right in our own skins of chemical change caused by the action of light. Tan also is due to pigment in the skin and is caused by light. ”

“ Between the two is placed the mucous layer, of which the pigment alone in reality varies in quantity and colour according to the race.
All the colours presented by the human skin have two common elements, the white of the dermis and the red of the blood. Moreover, each has its own proper element, resulting from the colourings of the pigment. The rays reflected from these different tissues combine into a resultant which produces the different tints and traverses the epidermis. ”

“ As with the painter, next to line comes color. Every one, of course, knows that a fresh, rosy color is usually associated with health, while a pale, sallow complexion suggests disease. But our color signals, while more vivid, are much less reliable and more apt to deceive than our line-markings.
Surprising as it may sound, careful analyses have shown, first, that the kind of pigment present in the human skin of every race is absolutely one and the same. The only difference between the negro and the white man is that the negro has two or three times as much of it. ”

“ The most ordinary way, however, in which the pigment is found is when it exists in the depths of the tissues reduced to very fine particles, best seen under the microscope. When scattered, they scarcely influence the shade; but, when close together, they are very perceptible. This explains the color of the negro: under the very delicate layer of skin which is raised by a slight burn there may be seen abundance of brown pigment in the black man. It is quite superficial, for the skin differs only from that of the European in tone; it wants the exquisite transparency of fair races. ”

“ Among the Jews who have settled in Northern Europe, are many of light complexion, while those who live in India are as dark as the Hindoos. Intense heat also increases this coloring matter, and thus a furnace-man's skin, even where protected by clothing, becomes completely bronzed. The black pigment has been known to disappear during severe illness, and a lighter color to be developed in its place. Among the negroes, are sometimes found people who have no complexion, i. e., there is no coloring matter in their skin, hair, or the iris of their eyes. ”

“ The colours of these cells blend with that of the blood, thus producing, according to their number and depth of coloration, the brunette, black, yellow, or red complexion. The palm of the negro’s hand is whiter than the rest of his body, because there the horny epidermis is so thick that the black pigmentary matter cannot be seen through it. And the reason why every negro is born to blush unseen is because the pigmentary matter in his skin is so deep and abundant that it neutralises the colour of the blood. ”

“ The hair, which was at first light blonde, with a yellow tinge, became chestnut brown in the course of a month and almost a pure black in six months, and acquired a more vigorous and thicker growth. A microscopic examination showed that the change in color was due to an increase of the normal pigment, and not to a dye. The eyes also became darker. The hair of an infant, treated for croup, showed a distinct change to a darker color after ten days' use of pilocarpine. ”

“ When we use these as pigments, we must remember that the pigment particles have a certain degree of transparency so that light partly penetrates them, certain rays being then reflected and certain absorbed according to the hue. A blue pigment, for example, absorbs all constituent rays of white light except the blue and the hues which border on blue in the spectrum, it being impossible to procure pigments which are so pure that they do not let some other hues besides their own characteristic one pass through them. ”