"These two sciences. the Science of Language and the Science of Man, cannot. at least for the present, be kept too much asunder; and many misunderstandings, many controversies, would have been avoided. if scholars had not attempted to draw conclusions from language to blood, or from blood to language. When each of these sciences shall have carried out independently its own classification of men and languages, then, and then only, will it be time to compare their results; but even then, I must repeat, what I have said many times before, it would be as wrong to speak of Aryan blood as of dolichocephalic grammar.(61)"
January 1, 1970
https://en.wikiquote.org/wiki/Max_M%C3%BCller