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540 the Brain," in which he exposed the unscientific character of the claims of phrenology. In this paper he also extended the idea of reflex nervous function to the centers of sensation and ideation, and enunciated the fundamental notions of "consensual" and of "ideo-motor" action. Curiously Mr. Carpenter's arguments converted the author of the book, Dr. Noble, who in a short time surrendered the principal hypotheses which he had endeavored to enforce in it.

His first systematic work, produced in 1839, was the "Comparative Physiology," or, to cite it by its full title, the "Principles of General and Comparative Physiology, intended as an Introduction to the Study of Human Physiology, and as a Guide to the Philosophical Pursuit of Natural History." This work, which has passed through many editions, and is even now, though out of print, hardly behind the times, is acknowledged to have been when it was first published the best arranged and most clearly written work on physiology in the English language. It was a pioneer and successful effort to deal with the phenomena of animal and vegetable life as parts of a single whole in the manner that is now almost universally done in treating of the science of biology. While residing at University Hall, from 1851 to 1859, he remodeled this work and divided it into two parts: the "Comparative Physiology," comprehending the general biological portion; and the "Human Physiology," consisting of the part relating to the special physiology of man and the higher animals. The "Human Physiology" embodied the most complete and thorough exposition of the subject that had yet been presented, and was particularly remarkable for the manner in which the physiology of the brain and nervous system was treated, and for the introduction of the theories of cerebral localization which have since been elaborated with increasing exactness and remarkable results. The part of the book relating to this branch of the subject, developed and matured by subsequent studies, was published separately in 1874 as the "Principles of Mental Physiology," a book which "Nature," in its review of it, characterized as marking the author as one of those philosophers "who refuse to treat the phenomena of mind as though they were in no way connected with the body through which they find their expression." Rejecting the method of treating mental phenomena as abstracted from their surroundings. Dr. Carpenter based his system on the construction and working of the nervous system. "But while shunning the metaphysical system," the reviewer in "Nature" continues, "he does not adopt the other extreme, the doctrine, we mean, of the thorough materialist, who regards all mental phenomena without exception as the outcome of previous physical causes which necessarily produce certain results. He steers a middle course, inasmuch as, while he advances the theory 'of the dependence of the automatic activity of the mind upon conditions which bring it within the nexus of physical causation,' he yet believes in 'an independent power controlling and directing that activity which we call will.'"