The difference between the maximum and minimum in the same race is also very striking. When it exceeds ten, M. Broca seems to attribute it almost exclusively to crossing. He has made an ingenious application of this idea in the history of the crossing of the Franks with the races who preceded them in France. But we can scarcely allow that this is always the case when we see the difference rising to 21·98 in the Negroes of West Africa, and to 25·05 in the Hottentots and Bosjesmans. It seems to me that this is only the repetition of a fact which we have already proved with regard to the capacity of crania.
M. Broca has made use of his nasal index to divide all human races into three groups from this point of view. In races of a mean nasal index, or Mesorhinian, it only varies from 48 to 53. Below these are ranged races with a long narrow nose, or Leptorhinian; and above, those with a broad and more or less flat nose, Platyrhinian.
The groups thus obtained are fairly homogeneous. The Leptorhinian would comprise only Whites, if the Esquimaux had not most unexpectedly stepped in. The Platyrhinian group is composed exclusively of Negroes, and includes all the races of this type studied by M. Broca, with the exception of the Papuans, who are perhaps a mixed race. The Mesorhinians embrace all the Yellow races, as well as the Polynesians, all the Americans and the Papuans, which I have just mentioned. We also find in this group Allophylian Whites, the Esthonians, and the Finns, who are thus separated from the Aryans and Semites.
In short, if we take means alone into consideration, the nasal index, taken as a basis in the division of races, breaks a much smaller number of natural relations than the characters which we have as yet discussed. Apart from the exceptions which I have just alluded to, intercrossing here only appears between races belonging to the same type. But as soon as we take individual variations into account, the mixture, so often observed, reappears.
M. Broca has studied the nasal index not only in the adult, but also when in a state of evolution. He found that in an embryo of three months this index was 76·80; in a perfect fœtus, 62·18; in a child of six years, 50·20; in modern Parisians, 46·81. Thus the index constantly diminishes as the body approaches its definite form. Our author concludes from this fact that the variations observed in the same race may often be referred to an arrest of development, or rather an arrest of evolution, and he seems disposed to attach the platyrhinism of Negroes to the same cause. He thus adopts the idea of Serres upon the general character of the Negro, which ideas we shall examine presently. This I regard as a very correct explanation of the origin of one of the distinctive features which most clearly distinguishes the black race. It is not, however, to the nasal index alone that this fact is applicable, as I have already proved.
The orbital index, also studied by M. Broca, is obtained by multiplying the vertical diameter of the orbit by 100, and dividing the product by the horizontal diameter. Considered from this point of view, races are divided into three groups, namely, the megasemes, whose mean index rises to 89 and higher; the mesosemes, whose index varies from 83 to 89 only; and the microsemes, whose index fall below 83.
The highest mean index stated by M. Broca, is found in the Aymaras, in whom it rises to 98·8. But we know that the cranium is artificially deformed by this people, and the practice may in some measure influence the form of the orbit. The maximum in normal skulls was observed in the Polynesians of Hawaï, where it was 95·40. The minimum of 77·01 is presented by the Guanches of Teneriffe.
The mean maximum variation is then 18·30.
But here, as in all other cases, individual variations are much more considerable. Without even taking the Aymaras into consideration, whose index sometimes exceeds 109, M. Broca found 108·33 in a Chinese, 105 in a Chinese and an Indian Red-Skin, 100 in two women of the Marquesas Islands, a Peruvian woman, a Malay, a Mexican, an Indo-Chinese, a woman of ancient Egypt, of Auvergne, and Paris. It is unnecessary to insist upon the meaning of these similarities.
The smallest orbital index known is that of the old man of Cro-Magnon, which we have seen to be 61·36. Above the latter, and at small distances from each other, may be ranged a Tasmanian, a Merovingian, the Mentone man (of the same race as that of Cro-Magnon), a Guanche of Teneriffe, a New Caledonian, an Australian, a Nubian, a Kaffir, a Spanish Basque, an Auvergnat, and lastly, the woman of Cro-Magnon, whose index is 71·25.