“ In 1810 he settled at Bristol as a physician, and in 1813 published his Researches into the Physical History of Man, in 2 vols., afterwards extended to 5 vols. The central principle of the book is the primitive unity of the human species, acted upon by causes which have since divided it into permanent varieties or races. The work is dedicated to Blumenbach, whose five races of man are adopted. But where Prichard excelled Blumenbach and all his other predecessors was in his grasp of the principle that people should be studied by combining all available characters. ”

“ One investigation begun in this work requires special mention, the bringing into view of the fact, neglected or contradicted by philologists, that the Celtic nations are allied by language with the Slavonian, German and Pelasgian (Greek and Latin) , thus forming a fourth European branch of the Asiatic stock (which would now be called Indo-European or Aryan) . ”