Licence: Public Domain Mark
Credit: The works of John Hunter / edited by James F. Palmer. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![challenged to fight a duel, volition, and reason determine me to go to it; but when at the place, my joints tremble, my stomach turns sick: this is the effect of mental impression, or feelings of the mind. The two operations are very different; and in general the feelings of the mind, if strong, will prevent all reasoning. Much more has been given to the brain and nerves than they deserve*. They have been thought to be the cause of every property in an animal body; that independent of them the whole body was a dead machine, and that it was only put in action by them. But although their actions are absolutely necessary in the machine, they are not so universally so as has been imagined. They are not the cause of growth, nor do they even preserve a part from death, although the whole as a whole cannot live without them. The nerves have but one mode of action, namely, that of conveying impressions ; but this in two different directions : one from their extre- mities in the body towards the brain, conveying impressions made on them to the brain, in order to excite actions suitable to these impres- sions ; the other, from the brain to the extremities, conveying the man- dates of the will, &c. That mode of action which is from the body towards the brain is of two kinds. One is the internal feel of the body, of perfection, imper- * [It may here be remarked, that the author, on the whole, lays less stress on the nervous system in his physiology than it probably deserves, at the same that he gives disproportionate importance to the stomach. Modern experiments have shown that the functions of digestion, nutrition, secretion, circulation, respiration, &c. in the higher animals are intimately dependent on the integrity of the brain and nervous system; and though in some of the lower animals no traces of this system are discoverable, yet may we safely infer, from the irritability which these animals manifest, that something corresponding to a nervous system actually exists, constituting the materia vita; diffusa of the author. Something analogous to this has been suspected in regard to the stomach itself, in certain species of zoophytes, in which either there are no visible stomachs or else the parts which are generally considered as separate and independent animals are regarded by others as merely a multiplication of stomachs belonging to the same indi- vidual. Some experiments also have lately been performed in America which show that undressed animal food undergoes a species of imperfect digestion when inclosed in fresh wounds: from which it seems probable, that notwithstanding the centralization of the vital organs in the higher orders of animals, the separate parts still exhibit traces of those vital endowments which in the lowest order of animals are diffused through the whole body, very much in the same manner as in vegetables. The proper objects of comparison however, in the present case, are the stomach with the great sympathetic nerve or nerves of the viscera rather than with the cerebral masses. The superaddition of the latter has reference principally to the organs of external relation, very few of which exist in zoophytes and the simpler forms of beings. Physiologically, it is as difficult to conceive of sensibility and contractility without a nervous system, or something ana- logous to this system, as it is to conceive of nutrition without digestive and circulatory organs.]](https://iiif.wellcomecollection.org/image/b21996623_0001_0290.jp2/full/800%2C/0/default.jpg)
