Let us return to anatomical differences, and to that which has, since antiquity, most vividly struck the masses, as well as serious investigators. We are going to speak about those colours in the skin of man which run through almost the whole of the chromatic scale, from dead white to the deepest brown.[128] There is no system which has not been thought of in order to explain these differences, even up to the influence of Noah’s curse.[129] Unfortunately, we are wanting in those histological and chemical researches which are necessary in order to form the bases of a complete history of the colours of the skin in the human race.[130] We can merely say, that the recent works upon certain morbid states, such as Addison’s disease, and others which may approach it, by making us acquainted with the pathological circumstances under which the European with a white skin becomes almost as black as a Negro, and by identical anatomical modifications, have nearly proved that atmospheric phenomena have not the influence which monogenists give to them, and that the first origin of the colour of the epidermis in the human race resides rather in the depths of the organism, inaccessible to celestial radiation.[131] The varieties which the pilous system presents is the chief point, and equal at least in importance to those of the cutaneous system. If we think that a classification of races, based simply upon the characteristics of the hair, as has been proposed,[132] would leave much to be desired, and would be far too artificial, we do not doubt, however, but that the pilous system can furnish indications of great value when they have been combined in a wise manner with other characteristics, as Isidore Geoffroy Saint-Hilaire has done.[133] Doubtless, the colours of the hair, from flaxen to black, and from brown to red, are innumerable in France, and as generally so in countries where the mixture of races has been carried as far as possible; but it must be remembered that among a purer population, less mixed with foreign blood, the constancy of characteristics taken from the hair is remarkably great.[134] Besides, the differences which present themselves do not relate merely to colour; the hair of a race of men may be either smooth, or woolly, or crisped, for in general these two latter terms are wrongly and indifferently used, when they ought really to point out two particular and distinct states. It is thus that the inhabitants of Lower Nubia, for instance, who have a very deep shade of colour, possess curled hair, truly _woolly_, and quite different to that of the Negro, whose hair is really _crisped_.[135] Other characteristics may be demanded from the length of the hair, from its transverse section,--the figure of which may vary considerably,--from its flexibility or its quantity; in fact, even from its manner of being placed in the head, the arrangement of which upon the scalp has never been properly studied, and which may, perhaps, vary