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The work by which Dr. Prichard's name is best known out of his 

 own profession, is entitled ' Researches into the Physical History of 

 Mankind.' The first edition was published in 1813, but the germ 

 of it was his Inaugural Thesis * De Humani Generis Varietate,' 

 printed in 1810. It went through two more editions, each havii^ 

 been entirely re-written. The third was extended into five closely 

 printed volumes, and was only completed in the year 1847. This 

 work is an extensive collection of facts regarding the origin, dis- 

 tribution, history and characters of the different tribes of man ; 

 but the facts are so arranged as to illustrate the great argument 

 which runs through the whole treatise, as to the unity of the species. 

 He made a most comprehensive inquiry into the laws which govern 

 the origination and dispersion of all organized beings, especially as 

 to the question whether each species in the animal and vegetable 

 world exists only as the progeny of one race, or has sprung origi- 

 nally from several distinct sources ; and arrived at the conclusion that 

 the various tribes of organized beings were originally placed by the 

 Creator in certain regions for which they are by their nature pecu- 

 liarly adapted ; each species having had its beginning in a single pair, 

 and the progeny having been left to disperse themselves according 

 to their locomotive powers, or their capabilities of bearing changes 

 of climate. He argued by analogy that if the races of men belong 

 to one species in the zoological sense,- it is extremely improbable 

 that they have descended from more than one stock, especially as 

 their locomotive powers, aided by the resources of human sagacity, 

 are greater than those of brute animals. That they are of one spe- 

 cies, he proved by those criteria of identity of species which are af- 

 forded : — 1. By the principal laws of the animal economy, particu- 

 larly those governing the duration of life, the period of utero-gesta- 

 tion, and the phenomena of reproduction; '2,. By like pathological 

 tendencies ; 3. By the fertility of mixed breeds. A very cogent 

 argument in the same direction was derived from the comparison of 

 the psychical qualities of species, as it appears that the species which 

 are most similar to each other and belong to the same genus, are 

 endowed with instincts even more distinct and characteristic than 

 peculiarities of bodily structure. An extensive survey of the human 

 races in this point of view shows that even the most dissimilar are 

 all possessed of common affections and sympathies, and are subjected 

 to precisely analogous laws of feeling and action, and that there- 

 fore, in so far as this evidence goes, they belong to one species or 

 lineage. As to the differences in colour, integument, hair, form 

 and structure, he showed that no remarkable instance of variation is 

 discoverable in mankind of which a parallel may not be found in 

 the varieties which arise in the species of the lower animals. These 

 several analogical arguments were confirmed by the historical in- 

 vestigation of the different races of men, in which the author took 

 occasion to show that all the different physical and psychological 

 characters, which had been before proved by analogy to be within 

 the limits of mere variation in species, have actually arisen in re- 

 peated instances, and have generally displayed themselves under the 



