General therapeutics and materia medica: adapted for a medical text book (Volume 2).

  • Dunglison, Robley, 1798-1869.
Date:
1843
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Licence: Public Domain Mark

Credit: General therapeutics and materia medica: adapted for a medical text book (Volume 2). 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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    discontinued without detriment, whilst the latter can only be cautiously pretermitted, especially it their employment has been persevered in for some time. Tonics are usually defined to be—Agents, which give strength and vigour to the body. In this point of view, all strengthening aliments might fall under the division. These are, in reality, tonics; but, as before observed, the consideration of aliments is not comprised in the objects of this work. It has been attended to elsewhere, [Elements of Hygiene, p. 205). By many therapeutical writers, tonics have been conceived to act by improving the tonicity of the muscular system; and, in the classification of Dr. A. T. Thomson, they are separated from ex- citants proper, and classed with astringents, under the head of— 1 Vital agents, influencing the body generally by operating directly on the muscular and sanguiferous systems.' Yet, he subsequently affirms, that tonics act on the vital principle through the medium of the nerves, and as far as their mode of operating is understood, we may regard them as excitants. To elucidate his ideas on the modits operandi of tonics, he has the following observations:—When an individual is in good health and in vigour of body, the muscles or moving organs feel firm and tense; they act regularly and powerfully, whether they are involuntary muscles, or those under the control of the will. This is a state of healthful tone. On the contrary, when the muscles feel soft and flabby, when the action of the involuntary muscles is languid, and the voluntary do not rapidly respond to the will; when there is a strong inclination for rest and indulgence; and when the movements of the body or its parts are performed with difficulty, this is a state of deficient tone or debility. That both these states are connected with the condition of the muscular fibre may be demonstrated by detaching a muscle from the bodies of two animals, in these opposite conditions, and ascertaining its strength by appending weights to it: the muscle taken from the healthy animal, or that in a state of'tone, will sustain a much greater weight than that which is in the opposite state. Thence, to a certain extent, lone implies a dilference in the mechanical condition of muscles; a greater degree of density and cohesion of their component fibres; but this must be also joined with elasti- city, that is, the power of resisting extension, and of restoring itself when the extending cause is removed, before the part can be said to be in the state of perfect tone. That this state is truly the result of vital energy is evident; for the same muscle loses the power of sustaining the weight, which it supported when first cut from the body, and this in proportion to the distance of time from that of its separation from the living body,—and he adds: medicines or medical agents, which produce this state of health- ful tone, and renew the tension and vigour of the muscular fibre, are thence denominated tonics.''