This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
This is an invaluable tonic measure in debility. There arc two kinds of exercise, which, though they produce the same ultimate effect, operate in a somewhat different manner, and are calculated to meet somewhat different indications; active, namely, and passive. Active exercise is that pin-formed under the influence of the will; passive, that in which the will is quiescent, and extraneous influences operate. Walking, running, leaping, wrestling, rowing, and the various gymnastic movements are examples of the former; riding on horseback, driving, steaming, sailing, etc., of the latter. The two are frequently more or less combined.
* The noted "extractum carnis" of Liebig, which has the advantage of containing little gelatin, is prepared by digesting meat, finely divided, and deprived as far as possible of gelatinous and fatty matter, with twice its weight of water, at 212°, for an hour, and separating the liquid by strong pressure; again, digesting and expressing as before; then evaporating to about one-sixth; and, after allowing the residue to cool, removing the fat that congeals on the surface, and finally evaporating to the ordinary consistence of extracts. Ten pounds of meat should yield six ounces of extract. (Pharm. Journ. and Trans., Oct. 1865, p. 207.) - Note to the third edition.
Raw meat. Considerable attention has of late been paid to raw meat and alcohol as a remedy for phthisis and other cachectic affections, introduced into use by M. Fuster, of Montpellier, France, who claims to have obtained great advantages from it. For the mode of administration, see my work on the Practice of Medicine (6th ed., i. 113). According to M. Fuster, the raw meat favours assimilation and nutrition, and with alcohol has proved of great advantage in various diseases besides phthisis, as chronic anaemia, leucocythemia, albuminuria, diabetes, and typhus and typhoid fevers. How much of the virtues of the remedy depends on the rawness of the meat is exceedingly doubtful; and it is liable to this great disadvantage, that the meat may contain the germs of one of the forms of taenia, or even those of the Trichina spiralis, and if taken uncooked, may give rise to those serious forms of parasitic disease. (Note to the third edition).
Thus, in the active exercise of rowing, while the muscles of the extremities are operating under the will, the whole frame is jarred by the movements of the boat; and in the passive exercise on horseback, while the body is shaken by the motions of the horse, the muscles are employed in regulating the animal, and maintaining the position of the rider. Active exercise is always primarily partial; passive is usually general, affecting every part of the body, though this is not necessarily the case in all instances; for a part only of the body may be agitated; as in that kind of exercise of the stomach recommended by Halsted in the treatment of dyspepsia, in which, the body being bent, and the hands pressed backward beneath the epigastrium, gentle and quickly repeated succussions are given to the organ by the upward movement of the fingers.
It is not difficult to explain the tonic effects of exercise. In the active variety, the cerebral centres are first stimulated; then the muscles; then the heart through the organic nervous centres; and finally all the functions indirectly, in consequence of the greater rapidity of the blood flowing everywhere through the capillaries, to which these functions are indebted for the supply at once of stimulus and material. A certain amount of exercise, varying according to the state of the individual, is requisite to support the functions in a condition corresponding with the degree of general strength. A moderate excess beyond this amount will produce only a moderate stimulation, or in other words a tonic effect; a great excess gives rise to proportional excitement, and may prove powerfully stimulant. The general laws above given, in reference to tonic medicines, are applicable to this remedial measure. In a state of debility, if the exercise be moderately increased, it will increase strength, by supporting all the organic functions, and among the rest digestion, sanguification, and nutrition. In perfect health, if urged beyond the point requisite for the sustenance of this condition, it leads to the evils before described as the result of the abuse of tonics. In either case, if used in great excess, so as to stimulate actively, it exhausts the excitability, and may thus lead to secondary prostration and debility. It is perceived, therefore, that the employment of active exercise as a tonic requires the same judgment and discrimination as that of the medicines belonging to the class. The general rule is to proportion the amount of it to the strength, and never to push it so far as to occasion secondary exhaustion. A slight feeling of fatigue may be considered as au evidence that it has been carried sufficiently far for the time.
In passive exercise, as a general rule, all parts of the body are excited by the agitation equably and moderately. The blood and nervous power are, therefore, invited in a nearly equal degree to the seat of every function, and a moderate diffusive tonic effect is experienced throughout the system. It may be said that, as there is only a certain quantity of blood, and a certain amount of nervous power in the body, you cannot increase these, in the system at large, through any immediate influence, and, therefore, that such a diffusive tonic effect as I have referred to is impossible. But the whole nervous power is never called into full exercise in health, and, though it cannot be indefinitely drawn upon, yet it may be so in a moderate degree, beyond the ordinary wants of the system; and its influence, therefore, may be everywhere in the same degree augmented. In reference to the blood, if the whole quantity cannot be increased, yet the rapidity of its motion may; so that a greater amount is present within a given time in all the organs. Besides, so far as concerns the smaller vessels or capillaries, where alone the blood is operative in sustaining the functions, the quantity may certainly be increased at the expense of that in the heart and great vessels, which serve mainly for its conveyance, or in the spleen, which probably often acts as a mere receptacle. It is, therefore, quite possible that all the organic functions may be moderately excited at the same time; and this, I think, is the effect of passive exercise. In consequence of the equable and diffusive character of its influence, it has an advantage over active exercise in cases of great debility. In the latter, a slight excess of muscular action may call the heart into inordinate and even dangerous excitement. Patients greatly debilitated have sometimes fallen dead, upon slight exertion, in consequence of the excessive action and consequent speedy exhaustion of the heart; and, where there is no danger of such a result, there may be liability to serious congestions, to hemorrhage, and even to cardiac hypertrophy. So also, the encephalon may be inordinately stimulated through the influence sent up to it by the excited muscles, demanding through the nervous centres a supply of blood. Again, the over-excitement of particular organs leads to deficiency of action or depression in others; as shown in the result of violent exercise taken immediately after a full meal; the powers of the system being concentrated in the muscular, and its immediately subsidiary functions, and withdrawn from the digestive, so that the food remains unacted on. In short, the influence of active exercise is necessarily more or less partial, and therefore liable to occasion local excess or deficiency of function; that of passive exercise is general, and more equable, and therefore safer when the object is to correct great general debility, especially when associated with morbid tendencies of any organ, as of the heart, which active exertion may serve to aggravate, or call into operation.