that of experiment by reproduction. This method, to some extent, combines physiological analysis and synthesis, and enables us to establish by evidence and counter-evidence those relations which unite the organ with the function in cerebral manifestations. When the brain of the inferior animals is removed, the function of the organ is necessarily suppressed; but the persistence of life in these beings allows the brain to grow again, and, in proportion as the organ reproduces itself, we observe its functions reappear. The like experiment succeeds in the same way with superior animals, such as birds, in whom intelligence is much more developed. For instance, when the cerebral lobes of a pigeon have been removed, the animal at once loses its senses, and the power of seeking its food. Yet if the animal is artificially fed, it can survive, because its functions of nutrition continue unimpaired so long as their special nervous centres are left unharmed. Little by little the brain renews itself with its particular anatomical elements, and in the degree in which this restoration takes place we observe the animal's use of its senses, and its instincts and intelligence return. Here, I repeat with emphasis, the experiment is complete: there has been as it were both analysis and synthesis of the vital function, because the successive destruction of the different parts of the brain has successively extinguished its different functional manifestations, and because the successive reproduction of the same parts has caused the same manifestations to reappear. It is hardly necessary to add that the same thing happens as to all the other parts of the body which are susceptible of reproduction.
Diseases, which are at bottom nothing but vital perturbations caused by Nature instead of being produced by the hand of the physiologist, affect the brain according to the usual laws of pathology; that is to say, by occasioning functional troubles which always correspond to the nature and seat of the injury. In a word, the brain has its pathological anatomy exactly as all the organs of the economy have, and the pathology of the brain has its special series of symptoms, just as the other organs have theirs. In mental alienation we observe the most remarkable disturbances of the reason, furnishing in their study a rich mine for the researches of the physiologist and the philosopher; but the various forms of lunacy or madness are nothing more than disturbances of the normal function of the brain, and these alterations of function in the cerebral organ, as in all the rest, are combined with invariable anatomical alterations. If, under many circumstances, these are not yet understood, the blame must be laid wholly on the imperfection of our means of investigation. Besides, do we not find that certain poisons, such as opium and curare, paralyze the nerves and the brain, without being able to discover any visible alteration in the nerve-substance? Yet we are sure that such alterations exist; for, to admit the contrary, would be to admit an effect without a cause. When the poison has ceased to act, we find the mental disturbances disappear, and