The elements of materia medica and therapeutics (Volume 1).

  • Pereira, Jonathan, 1804-1853.
Date:
1843
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Licence: Public Domain Mark

Credit: The elements of materia medica and therapeutics (Volume 1). Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    a. On Vegetables.—A certain degree of heat promotes all the vital processes of plants. It accelerates germination, the growth and development of all vegeta- ble organs, inflorescence, fecundation, and the ripening of the fruit; and it quickens the.movements of parts susceptible of motion. Too elevated a tem- perature, accompanied with dryness, deranges the health of plants. (Decan- dolle, Physiologic Vegetale, torn. iii. p. 1098.) An intense heat decomposes the vegetable tissues. b. On Man and other Animals.—A certain degree of external heat (different in different beings) promotes the vital manifestations of animals, and hence we denominate it an excitant or stimulant. .Its prolonged operation, however, is followed by debility and exhaustion proportionate to the previous excite- ment. The influence of tropical heat on the human species furnishes an illustrative example of the effects just mentioned. It is well known that the mental powers of children are sooner developed, and the sexes arrive earlier at puberty, in warm than in cold countries. Moreover, the languor, indolence, and relaxed fibres, so commonly observed in the inhabitants of tropical climates, are probably to be ascribed, in a great measure, to the exhausting and enervating influence of external heat. The effects of topical heat are first, a sensation of warmth, redness, turgescence, and a slight augmentation of temperature of the part heated. The diameters of the minute capillary vessels expand under the influence of caloric, and thus the red blood-disks are enabled to enter tubes previously impervious to them. The augmented volume of the part arises, therefore, in a great measure from the pre- sence of an increased quantity of blood; but in part also from the dilatation of the solids and fluids caused by their augmented temperature. The living tissues become more relaxed, soft, and flexible, under the influence of a moderate heat, and admit of a more rapid transpiration. A more violent degree of heat causes burning pain, redness, and vesication. A still more intense heat destroys vitality and organization. Whenever a large portion of the surface of the body is destroyed (as in burns and scalds,) great constitutional disturbance, or even death, results from the shock given to the ner- vous system. If the whole body be subjected to an elevated temperature, not incompatible with prolonged life, its effects are manifested first in the vascular system, and in the organs connected therewith. The superficial vessels enlarge; the skin be- comes redder; and the pulse quicker and fuller: respiration more frequent; the animal heat is augmented; and the expired air is hotter, and more loaded with vapour. The exciting influence of heat, on the vascular system, points out the impropriety of em- ployin<r this agent in inflammation or congestion of the organs (heart and lungs) eno-aged in the circulation of the blood ; in dilatations of the heart; in aneurism ; in apoplexy; and many other cases which will readily suggest themselves. Increased exhalation (first of insensible and vaporous matter, then of visible and liquid sweat) and augmented secretion of the periphery soon succeed. The rapid conversion of a liquid into an aeriform fluid (insensible perspiration) is attended with the production of cold; and thus animals are enabled to counteract external heat, and to maintain nearly their original temperature, when exposed to a temperature considerably higher than that of their own bodies, by the in- creased perspiration which they suffer under these circumstances. The deter- mination to the surface, and the increased transpiration and secretion of the skin are attended with a eontemporaneous diminution of activity in some of the inter- nal organs. Thus, the secretions of the kidneys and the mucous membranes are diminished in consequence of the increased secretion and exhalation of the skin. Tin- mutually antagonizing influence of determinations of blood to different parts as well as of the secretions of different tissues—is a circumstance the knowledge of which is of <rreat