Its effects would probably have been greater in respect to the quant.i.ty breathed, if it had been given in a dilute state, mixed with 10 or 20 times its quant.i.ty of atmospheric air, as otherwise much of it returns by expiration without being deprived of its quality, as may be seen by the person breathing on the flame of a candle, which it enlarges. See the Treatise of Dr. Beddoes above mentioned.

V. Those pa.s.sions, which are attended with pleasurable sensation, excite the system into increased action in consequence of that sensation, as joy, and love, as is seen by the flush of the skin. Those pa.s.sions, which are attended with disagreeable sensation, produce torpor in general by the expence of sensorial power occasioned by inactive pain; unless volition be excited in consequence of the painful sensation; and in that case an increased activity of the system occurs; thus paleness and coldness are the consequence of fear, but warmth and redness are the consequence of anger.

VI. Besides the exertions of the system occasioned by increased stimuli, and consequent irritation, and by the pa.s.sions of the mind above described, the increased actions occasioned by exercise belong to this article. These may be divided into the actions of the body in consequence of volition, which is generally termed labour; or secondly, in consequence of agreeable sensation, which is termed play or sport; thirdly, the exercise occasioned by agitation, as in a carriage or on horseback; fourthly, that of friction, as with a brush or hand, so much used in the baths of Turkey; and lastly, the exercise of swinging.

The first of these modes of exercise is frequently carried to great excess even amongst our own labourers, and more so under the lash of slavery; so that the body becomes emaciated and sinks under either the present hardships, or by a premature old age. The second mode of exercise is seen in the play of all young animals, as kittens, and puppies, and children; and is so necessary to their health as well as to their pleasure, that those children, which are too much confined from it, not only become pale-faced and bloated, with tumid bellies, and consequent worms, but are liable to get habits of unnatural actions, as twitching of their limbs, or of some parts of their countenance; together with an ill-humoured or discontented mind.

Agitation in a carriage or on horseback, as it requires some little voluntary exertion to preserve the body perpendicular, but much less voluntary exertion than in walking, seems the best adapted to invalids; who by these means obtain exercise princ.i.p.ally by the strength of the horse, and do not therefore too much exhaust their own sensorial power. The use of friction with a brush or hand, for half an hour or longer morning and evening, is still better adapted to those, who are reduced to extreme debility; and none of their own sensorial power is thus expended, and affords somewhat like the warm-bath activity without self-exertion, and is used as a luxury after warm bathing in many parts of Asia.

Another kind of exercise is that of swinging, which requires some exertion to keep the body perpendicular, or pointing towards the center of the swing, but is at the same time attended with a degree of vertigo; and is described in Cla.s.s II. 1. 6. 7. IV. 2. 1. 10. Sup. I. 3. and 15.

The necessity of much exercise has perhaps been more insisted upon by physicians, than nature seems to demand. Few animals exercise themselves so as to induce visible sweat, unless urged to it by mankind, or by fear, or hunger. And numbers of people in our market towns, of ladies particularly, with small fortunes, live to old age in health, without any kind of exercise of body, or much activity of mind.

In summer weak people cannot continue too long in the air, if it can be done without fatigue; and in winter they should go out several times in a day for a few minutes, using the cold air like a cold-bath, to invigorate and render them more hardy.

III. CATALOGUE OF THE INCITANTIA.

I. Papaver somniferum; poppy, opium.

Alcohol, wine, beer, cyder.

Prunus lauro-cerasus; laurel, distilled water from the leaves.

Prunus cerasus; black cherry, distilled water from the kernels.

Nicotiana tabac.u.m; tobacco? the essential oil, decoction of the leaf.

Atropa belladona; deadly nightshade, the berries.

Datura stramoneum; thorn-apple, the fruit boiled in milk.

Hyoscyamus reticulatus; henbane, the seeds and leaves.

Cynoglossum; hounds tongue.

Menispermum, cocculus; Indian berry.

Amygdalus amarus; bitter almond.

Cicuta; hemlock. Conium maculatum?

Strychnos nux vomica?

Delphinium stavisagria?

II. Externally, heat, electricity.

III. Ether, essential oils.

IV. Oxygen gas.

V. Pa.s.sions of love, joy, anger.

VI. Labour, play, agitation, friction.

ART. III.

SECERNENTIA.

I. Those things which increase the irritative motions, which const.i.tute secretion, are termed secernentia; which are as various as the glands, which they stimulate into action.

1. Diaph.o.r.etics, as aromatic vegetables, essential oils, ether, volatile alcali, neutral salts, antimonial preparations, external heat, exercise, friction, cold water for a time with subsequent warmth, blisters, electric fluid.

2. Sialagogues, as mercury internally, and pyrethrum externally.

3. Expectorants, as squill, onions, gum ammoniac, seneka root, mucilage: some of these increase the pulmonary perspiration, and perhaps the pulmonary mucus.

4. Diuretics, as neutral salts, fixed alcali, balsams, resins, asparagus, cantharides.

5. Cathartics of the mild kind, as sena, jalap, neutral salts, manna. They increase the secretions of bile, pancreatic juice, and intestinal mucus.

6. The mucus of the bladder is increased by cantharides, and perhaps by oil of turpentine.

7. The mucus of the r.e.c.t.u.m by aloe internally, by clysters and suppositories externally.

8. The mucus of the cellular membrane is increased by blisters and sinapisms.

9. The mucus of the nostrils is increased by errhines of the milder kind, as marum, common snuff.

10. The secretion of tears is increased by volatile salts, the vapour of onions, by grief, and joy.

11. All those medicines increase the heat of the body, and remove those pains, which originate from a defect of motion in the vessels, which perform secretion; as pepper produces a glow on the skin, and balsam of Peru is said to relieve the flatulent cholic. But these medicines differ from the preceding cla.s.s, as they neither induce costiveness nor deep coloured urine in their usual dose, nor intoxication in any dose.

12. Yet if any of these are used unnecessarily, it is obvious, like the incitantia, that they must contribute to shorten our lives by sooner rendering peculiar parts of the system disobedient to their natural stimuli. Of those in daily use the great excess of common salt is probably the most pernicious, as it enters all our cookery, and is probably one cause of scrophula, and of sea-scurvy, when joined with other causes of debility. See Botanic Garden, Part II. Canto IV. line 221. Spices taken to excess by stimulating the stomach, and the vessels of the skin by a.s.sociation, into unnecessary action, contribute to weaken these parts of the system, but are probably less noxious than the general use of so much salt.

II. OBSERVATIONS ON THE SECERNENTIA.

I. 1. Some of the medicines of this cla.s.s produce absorption in some degree, though their princ.i.p.al effect is exerted on the secerning part of our system. We shall have occasion to observe a similar circ.u.mstance in the next cla.s.s of medicines termed Sorbentia; as of these some exert their effects in a smaller degree on the secerning system. Nor will this surprise any one, who has observed, that all natural objects are presented to us in a state of combination; and that hence the materials, which produce these different effects, are frequently found mingled in the same vegetable. Thus the pure aromatics increase the action of the vessels, which secrete the perspirable matter; and the pure astringents increase the action of the vessels, which absorb the mucus from the lungs, and other cavities of the body; hence it must happen, that nutmeg, which possesses both these qualities, should have the double effect above mentioned.

Other drugs have this double effect, and belong either to the cla.s.s of Secernentia or Sorbentia, according to the dose in which they are exhibited. Thus a small dose of alum increases absorption, and induces costiveness; and a large one increases the secretions into the intestinal ca.n.a.l, and becomes cathartic. And this accounts for the constipation of the belly left after the purgative quality of rhubarb ceases, for it increases absorption in a smaller dose, and secretion in a greater. Hence when a part of the larger dose is carried out of the habit by stools, the small quant.i.ty which remains induces costiveness. Hence rhubarb exhibited in small doses, as 2 or 3 grains twice a day, strengthens the system by increasing the action of the absorbent vessels, and of the intestinal ca.n.a.l.

2. Diaph.o.r.etics. The perspiration is a secretion from the blood in its pa.s.sage through the capillary vessels, as other secretions are produced in the termination of the arteries in the various glands. After this secretion the blood loses its florid colour, which it regains in its pa.s.sage through the lungs; which evinces that something besides water is secreted on the skins of animals.

No statical experiments can ascertain the quant.i.ty of our perspiration; as a continued absorption of the moisture of the atmosphere exists at the same time both by the cutaneous and pulmonary lymphatics.

3. Every gland is capable of being excited into greater exertions by an appropriated stimulus applied either by its mixture with the blood immediately to the secerning vessel, or applied externally to its excretory duct. Thus mercury internally promotes an increased salivation, and pyrethrum externally applied to the excretory ducts of the salival glands.