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by which the functions of the body are performed. The natural, or least attenuated of the spirits, are evolved from the blood in the liver, the organ in which the blood itself is first elaborated. Conducted with the blood to the lungs, and there exhaling certain impurities, and combining with the respired air, the natural are converted into the vital spirits; and passing afterwards to the brain, the vital become still further attenuated and converted into the animal spirits.
The functions are also of three corresponding orders, the vital, the animal, and the natural. To the first of these belong the action of the heart and ' arteries, the passions of anger and revenge; to the second belong the intellectual powers, intelligence and sensibility; to the third belong the functions of nutrition, muscular action, and generation; and these functions he further divides into the external and internal. By the intervention of the pneuma, the vital force produces the pulsation of the heart and arteries. He undertakes to prove experimentally that an interspace exists between the lungs and pleura, in which the respired air is expanded. He holds that the blood is cooled, the pneuma relieved of its fuliginous particles, and the blood endowed with the vital force, by the process of respiration; and that this process is effected by means of the diaphragm and intercostal muscles.
The brain is the seat of the rational mind; the heart is the seat of courage and the angry passions; the liver is the seat of desire. By the internal pul
sation of the brain, the pneuma of the ventricles is engendered, and in these ventricles the functions of the mind are executed. The passage of the vital spirits from all parts towards the brain, where they acquire new qualities,, explains in what way the mind is influenced by the body. But it is not clear whether he looked upon the mind as an entity, or as a mere result of organic action. From the brain, by the agency of the nerves, sensibility and motive power are diffused throughout the body; but special forces subordinate to the mind, preside over the functions of special sense. The brain in the performance of its functions exudes a thin pituitous humor, which is discharged through the foramina in the cribriform plate of the ethmoid bone, and escapes through the throat and nostrils.
The natural functions are accomplished by the pneuma, through the medium of the blood. But every organ has its own peculiar forces of attraction, retention, and expulsion, analogous to the forces which have recently been called endosmosis and exosmosis. Thus, by its own peculiar power the stomach attracts the aliment, retains it, concocts it, or expels it. The genital apparatus of the two sexes differ only in this; that while in the male they are external, in the female they are wholly internal. The uterus has as many separate cavities as the animal has mammary glands. The seminal fluid is in the female from the ovaries; in the male, from the testes. The commingling of the two fluids results in a male or female foetus, according as the
fluids are from the organs of the right or left side. The placenta supplies the foetus with blood and pneuma. The brain, derived directly from the seminal fluids, is developed before the heart.
From this short exposition it will be seen, that his physiological opinions were mostly hypothetical. Yet in many points he entered into experimental inquiries for maintaining them. In this way he
established the influence of the nerves over the voluntary muscles; and the existence of red blood, instead of simple pneuma, in the arteries, a fact, however, known before his time.
In hygiene, his rules are characterized by minute refinements. Among the fundamental laws of health, he asserts that the different parts of the body are maintained in healthy action by those agencies and influences only with which they hold special relations. He distinguishes men into three classes: 1st, the naturally sound and rugged, living at ease, and able to bestow proper care upon their health; 2dly, those constitutionally feeble and delicate; lastly, those whose occupation obliges them to live irregularly. His four epochs of life-infancy, youth, manhood, and old age-have their respective tendencies and immunities; the last period he looks upon as for the most part a condition of disease. By carefully studying the circumstances of age and habit, in connection with the temperament, he establishes his rules of health. He examines in detail the influence and uses of what are called the non-naturals, air,
aliment, exercise, repose, and the like. His precepts in respect to these are judicious. He advises mothers to nurse their own offspring; he deprecates the practice of attempting to strengthen young infants by immersing them in cold water, as sometimes advised. He was an advocate for a rigid diet, and insists that no occupation should be allowed to interfere with regular daily exercise.
In Pathology, he was aware of the importance of tracing the general symptoms of disease to the organs or parts primarily affected. This study he has illustrated in his treatise De Locis Affectis, the ablest of his pathological works. He makes health to consist in freedom from pain, and in the easy. and unembarrassed exercise of all the functions; implying in this an equable intermixture of the four elements, and proper relation between the solids and fluids. Disease, on the contrary, he makes to consist in a disturbed condition of one or more of the functions. The diathesis, or predisposition to disease, he distinguishes from the disease itself. The diseases of the simple parts depend in general on disproportion in the union of their elementary constituents. The distemper itself may be either material, or independent of matter. The symptoms of disease are the result of derangement of function, or of change in the apparent qualities, or of disordered secretions. The causes of disease are external and internal. The former, or the Procatartic, are necessary to give play to the second, which are subdivided into the antecedent and the
conjoint. The most frequent of the internal causes is the superabundance or the degeneration of the humors.
Plethora is the result of a relative or absolute superabundance of blood. Cacochymia is from the superabundance of the other humors by which the blood becomes corrupted. Every alteration of the humors from their healthy condition is called a putridity. The heat developed by putridity gives rise to fever, by being communicated to the heart and arteries. With the exception of ephemeral fever, which depends on some particular alteration in the pneuma, all fevers arise from corruption of the humors. Among the intermittents, a quotidian arises from corruption in the phlegm; a tertian, from corruption in the bile; a quartan, from a corresponding condition of the atrabile. entrance of blood into parts which do not naturally contain it, gives rise to inflammation. If the blood thus enters simply, the inflammation becomes phlegmonous; if accompanied with pneuma, the inflam-. mation is pneumatous; if with the pituita or phlegm, it becomes oedematous; if with the yellow bile, erysipelatous; and if with the atrabile, scirrhous. Advocating the Hippocratic doctrine of critical days, he attempts to support it on grounds purely theoretical, and drawn from the periodical changes in nature, or the influence of the stars. His fondness for subtile refinement is nowhere more clearly seen than in his numerous and, as they must now be considered, fanciful divisions of the pulse.