It may be safely asserted, then, that on none of the foregoing characters can specific distinctions be justly based, since none of them possess the constancy which is required to give them such a rank ; and those which are most strongly marked in particular cases, are such as can be proved to be most liable to modification from external conditions.
4. We next have to inquire into the dis tinctions founded upon.the colour of the Skin; which, at first sight, appear to present a degree of constancy that gives them a strong claim to be regarded as permanent, and there fore as valid distinctive characters between the several races of mankind. The hue of the Skin, it is now well known, exists in the epidermis only, and depends upon the pre sence of pigmentary matter in the ordinary cells of that part. What was formerly known as the " rete mucosum," or " rete Malpighii," and described as a distinct colouring layer between the epidermis and cutis vera, is now known to be nothing else than the newest and softest layer of epidermis. There is no structure (as has been affirmed by some ana tomists) in the skin of the dark races, that is at all peculiar to it ; the very same dark matter being found in particular spots of the fairest skins, as in that of the areola sur rounding the nipple during pregnancy. The following is the description of the structure given by Messrs. Todd and Bowman, the accuracy of which the author can fully confirm from his own observation However vari ous in colour and hue, the colouring matter always consists of oblong or oval grains of extreme minuteness (I-20,000th of an inch in their long diameter), and occupying the interior of some of the epidermic particles. In the Negro it is accumulated in enormous quantity, and completely envelopes the nu clei immediately resting on the cutis. On examining a vertical section of the whole cuticle, we find the colouring matter gradually diminishing as we approach the surface ; and it is most clear that there is no true line of demarcation between the two portions. We may observe the colour of the rete muco sum deeper at points; and a greater propor tionate depth of colour is traceable over such points, through all the layers, as far as the sur face ; we may even discern a sort of stream of coloured grains advancing towards the surface. Hence there can be little doubt that the de crease of colour in the superficial laminm is due to that chemical change which has been described as gradually taking place in the interior of the epidermic particles." # Still it might be affirmed that the presence of a large amount of pigmentary matter, of a peculiar tint, in the substance of the epider mis, constitutes a typical character of par ticular races, even though there be no distinct pigmentary layer ; since spots and patches of colour are often admitted as specific distinc tions among the lower animals. Thus, for
example, it has been maintained that the fair and ruddy Saxon, the jet-black Negro, the olive Mongolian, and the copper-coloured North-American, have as good a claim to be ranked as distinct species, on the score of the uniform transmission of their respective hues from generation to generation, as have many races of Lepidoptera (for example) which are regarded by naturalists as specifi cally diverse on account of the distribution of colour in the scales of their wings. But as the validity of the specific distinction among these last entirely rests upon the intransitive nature of the character, the several individuals that constitute either race exhibiting no ap proximation towards those of the other, and the successive generations repeating the re spective peculiarities of each race with great exactness, we must apply the same test to the Human races.
Now, if we take any one of those groups of nations which are usually regarded as alto gether constituting a race, such as the (so called) Caucasian, the Mongolian, the African the American, or the Polynesian, it will be found that the greatest diversity of com plexion exists within its limits. Thus, among the " Japetic" races, — which are cha racterised by the possession of the oval type of cranial conformation, and whose languages are so clearly traceable to a common stock, that no philologist now questions the identity of their origin,—we find every range of colour, from the fair Saxon and Celtic nations, to the deep brown of the Indian, Brahmin.* Among the Syro-Arabian, or " Semitic" races, again, which are spread over South-western Asia and Northern Africa, and which are connected by close affinity of language, there is an equal variety of complexion. All travellers who have visited the high lands of Arabia, repre sent the inhabitants as having light com plexions, their eyes being often blue, and their hair red. The Arabs near Muscat are of a sickly yellow hue ; those of the neigh bourhood of Mecca are of a yellowish brown, while those of the low countries bordering on the Nile are almost jet-black. So, again, among the various tribes referable to the same stock, which inhabit the Atlantic region of the north of Africa, similar differences of com plexion prevail; for whilst those which inhabit the higher lands and mountain passes, such as the tribe of Mozabi among the Kabyles, are remarkably fair, those which dwell in the more level parts of the country are swarthy, and some of the Tuaryks which inhabit the borders of the Great Desert, are as black as the darkest Negro.