Peter's Hospital. Among his patients there were many lunatics, whose maladies especially interested him. But this book gave no indication of those new and striking conclusions respecting insanity which he developed later. An invitation to write an article on insanity in the ‘Cyclopædia of Practical Medicine’ led him to pursue the subject, and to publish in 1835 his ‘Treatise on Insanity and other Disorders affecting the Mind.’ This was long the standard work on this branch of medicine. Its leading interest lies in the assertion—in contradiction to the position Prichard had previously assumed—of the existence of a distinct disease of ‘moral insanity.’ This malady Prichard claims to have been the first to recognise and describe. He sought to prove that moral insanity was a morbid condition, not necessarily the concomitant or outcome of mental disorder or incapacity (see Library of Medicine, ed. Tweedie, ii. 110). He pointed out that there are patients truly insane and irresponsible, who suffer from moral defect or derangement, without such an amount of intellectual disorder as would be legally recognised either in a court of law or for the purpose of certification. He showed that madness often consisted ‘in a morbid perversion of the natural feelings, affections, inclinations, temper, habits, moral dispositions, and natural impulses, without any remarkable disorder or defect of the intellect or knowing and reasoning faculties, and particularly without any insane illusion or hallucination’ (Treatise on Insanity, p. 6). In face of the generally accepted view of the solidarity of the mental functions, the difficulty of accepting Prichard's doctrine is, from a psychological point of view, not inconsiderable. But despite the warm contests that have taken place in regard to Prichard's conclusion among both lawyers and physicians, his position has been confirmed by subsequent observers, and is accepted by leading scientific men in Europe and the United States. Esquirol, who at first opposed Prichard's views, was obliged, as he soon admitted, ‘to submit to the authority of facts’ (Des Maladies Mentales, 1838, ii. 98). Herbert Spencer has acknowledged his belief in moral insanity, which he does not consider irreconcilable with his well-known theories of psychology. Prichard's study of moral insanity induced him to prepare, in 1842, a work specially intended to indicate its bearing on legal questions, under the title ‘On the Different Forms of Insanity in relation to Jurisprudence, designed for the use of persons concerned in legal questions regarding unsoundness of mind.’
Still pursuing his anthropological researches, Prichard stated his chief results in his ‘Natural History of Man,’ which appeared in 1843. It comprised inquiries into the modifying influence of physical and moral agencies on the different tribes of the human family. He dwelt forcibly on the innumerable points of resemblance between man and the lower animals. He observed that ‘to many persons it will appear paradoxical to ascribe the endowment of a soul to the inferior tribes in the creation; yet it is difficult to discover a valid argument that limits the possession of an immaterial principle to man.’ He inquired whether man has not received, in addition to his mental sagacity, a principle of accommodation, by which he becomes fitted to occupy the whole earth, and to modify the agencies of the elements upon himself. Admitting that this is the case, he asks whether these agencies do not also modify him. There exists, however, the alternative opinion—that mankind is made up of races differing from each other from the beginning of their existence. The main object of Prichard's work was to determine which of these views was the better entitled to assent. His conclusion was very decided that ‘we are entitled to draw confidently the conclusion that all human races are of one species and one family’ (p. 546). Prichard's conclusion is that generally held by ethnologists of the present day.
Between 1836 and 1847 he brought out, in five volumes, ‘Researches into the Physical History of Mankind,’ and in 1855 appeared a fourth edition of his ‘Natural History of Man,’ 2 vols. In the words of Professor Tylor of Oxford, Prichard's work as an anthropologist is admirable; and it is curious to notice how nowadays the doctrine of development rehabilitates his discussion of the races of man as varieties of one species. We may even hear more of his theory that the originally dark-complexioned human race produced, under the influences of civilised life, the white man. Prichard's merit as the philologist who first proved the position of Keltic languages as a branch of the Indo-European has not met with due recognition; Adolphe Pictet, who made his reputation by a treatise on the same point, did not publish it until after Prichard's results on this topic had appeared in the ‘Eastern Origin of the Celtic Nations,’ 1831 (ed. R. G. Latham, 1857).
In an address before the Ethnological Society of London on 22 June 1847, ‘On the Relations of Ethnology to other Branches of Knowledge,’ Prichard asserted the importance of ethnology as a science, and ar-