I do not, however, mean to oppose Prichard on every point. One of his conclusions I gratefully adopt, namely that “difference of climate occasions very little, if any, important diversity as to the periods of life and the physical changes to which the human constitution is subject.”[67] This remark is very true, and I would not dream of contesting it. I merely add that it seems to contradict to some slight extent the principles otherwise upheld by the learned American physiologist and antiquary. The reader will not fail to see that the question on which the argument here turns is that of the permanence of types. If we have shown that the human races are each, as it were, shut up in their own individuality, and can only issue from it by a mixture of blood, the unitarian theory will find itself very hard-pressed. It will have to recognize that, if the types are thus absolutely fixed, hereditary, and _permanent_, in spite of climate and lapse of time, mankind is no less completely and definitely split into separate parts, than it would be if specific differences were due to a real divergence of origin. It now becomes an easy matter for us to maintain this important conclusion, which we have seen to be amply supported, in the case of the Arabs, by the evidence of Egyptian sculpture, and also by the observation of Jews and gipsies. At the same time there is no reason for rejecting the valuable help given by the paintings in the temples and underground chambers in the valley of the Nile, which equally show the permanence of the Negro type, with its woolly hair, prognathous head, and thick lips. The recent discovery of the bas-reliefs at Khorsabad confirm what was already known from the sculptured tombs of Persepolis, and themselves prove, with absolute certainty, that the Assyrians are physiologically identical with the peoples who occupy their territory at the present day. If we had a similar body of evidence with regard to other races still living, the result would be the same. The fact of the permanence of types would merely be more fully demonstrated. It is enough however to have established it in all the cases where observation was possible. It is now for those who disagree to propose objections.