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of the sensory nerves in the skin, though some act probably by
stimulating the local circulation, as in inflammation. The prin-
cipal members of this group are-
Faradism.
Chloroform.

Volatile Oils.
Heat.
Carbolic Acid.

Acrid Essential Oils.
Cold.
Creasote.

Metallic Salts.
Alcohol.
Mineral Acids.

Veratrine (at first).
Ether.
Ammonia.

Cantharis (at first).

Local Anæsthetics and Anodynes (dv, without, as you, perception, ošúrn, pain),-reduce the functions of the sensory nerves until they lose the power of receiving or conducting sensations. Some act by direct depression of the end-organs in the skin, etc., others by impairing the conductivity of the sensory nerves, while some act indirectly by reducing the local circulation. The Anodynes diminish, and the Anästhetics destroy, for a time, the sensibility of the skin or mucous membrane. The chief agents of this class areLocal Anodynes.

Local Anæsthetics.
Aconite, Aconitine.

Extreme Cold, Ice.
Belladonna, Atropine.

Ether Spray:
Opium, Morphine.

Carbolic Acid.
Carbolic Acid.

Erythroxylon.
Chloroform.

Cocaine.
Chloral.

Hydrocyanic Acid.
Veratrum, Veratrine.

Creasote.
Volatile Oils.

Oil of Turpentine.
Galvanism.

lodoform.

Cerebral Excitants,-are remedies which increase the functional activity of the cerebrum, without producing any subsequent depression, or any suspension of the cerebral functions. They act partly by increasing the action of the heart and consequently the rapidity of the circulation, partly by a direct action upon the gray matter of the brain. The chief members of this group areAlcohol (at first).

Coffee, Caffeine.
Ammoniac.

Tea, Theine.
Asafetida.

Guarana, Guaranine.
Camphor.

Erythroxylon, Cocaine.
Cannabis.

Tobacco.
Valerian.

Strychnine.
Ammonia (inhaled).

Acetic Acid (inhaled).

Deliriants excite the functions of the higher brain to such a degree as to disorder the mental faculties, producing intellectual confusion, loss of will-power, delirium and even convulsions.

AGENTS ACTING ON THE NERVOUS SYSTEM.

403

They are all narcotics (though all narcotics are not deliriants),
and may be listed as follows, viz. -
Alcohol.

Cannabis Indica.
Belladonna.

Chloral.
Stramonium.

Lupulus (at first).
Hyoscyamus.

Opium (at first).

Cerebral Depressants lower or suspend the functions of the higher cerebrum after a preliminary stage of excitement. Under this head may be included the Narcotics, General Anästhetics, and several of the Antispasmodics, all acting on the cells of the convolutions, at first stimulating the brain-functions, they produce after a time stupor, coma and insensibility.

The most useful of this class are the Bromides, Zinc and Caffeine, as they also diminish reflex excitability and thus secure rest of the nervous system. Some of them are decidedly dangerous, as they may paralyze the heart or the medulla and its centres of organic life before the consciousness is much disturbed; such being Chloroform, Aconite, Opium, and the irritant poisons.

Narcotics (vápur, stupor),—are agents which, at first excitant to the higher brain, produce profound sleep, characterized by stupor, and if the dose be sufficient coma, insensibility and death by paralysis of the medullary centres governing respiration and other functions of organic life. They are closely related to stimulants, Opium and Alcohol being good illustrations, in the different stages of their action, of both stimulant and narcotic effects. They give us the power of lowering perception, inducing sleep and soothing the vital functions by rest, all of which are means of great therapeutical value. The chief narcotics areAlcohol.

Cannabis Indica.
Opium, Morphine.

Humulus.
Belladonna, Atropine.

Chloroform, Ether, etc.
Hyoscyamus.

Chloral-hydrate.
Stramonium.

Croton-chloral.

Hypnotics (ürvos, sleep), -are remedies which produce sleep, and in this wide sense of the term the class would include the Narcotics and the Anästhetics, as well as those agents which may be termed Pure Hypnotics, which induce sleep by bringing the brain into a favorable condition therefor rather than by direct soporific action. In this sense the purest hypnotics are the Bromides, but artificial sleep may be produced by many other agents. The principal members of this class are the following:

Opium, Morphine, Narceine.

Sodium Bromide.
Chloral-hydrate.

Calcium Bromide.
Croton-chloral.

Lithium Bromide.
Cannabis.

Zinc Bromide.
Cannabin Tannate.

Potassium Bromide.
Hyoscyamus.

Monobromated Camphor.
Paraldehyde.

Lettuce.
Hops.

Lactic Acid.
General Anästhetics.

Analgesics (ày, without, älyos, pain), or Anodynes (åv, without, oùóvn, pain), -are remedies which relieve pain, either by direct depression of the centres of perception and sensation in the cerebrum, or by impairing the conductivity of the sensory nerve fibres. Opium is the most efficient of all analgesics, because it arrests the afferent impressions at every step of their track—at their formation, along the course of their conduction, and at the point where they impinge on the sensorium. The Local Anodynes have been described (ante, page 402), and the list of General Anodynes includes the following-named agents, viz.Opium, Morphine.

Aconite.
Belladonna, Atropine.

Chloroform, Ether, etc.
Cannabis Indica.

Conium.
Stramonium.

Chloral-hydrate.
Hyoscyamus.

Croton-chloral.
Gelsemium.

Lupulus.

Anæsthetics (dy, without, a?o 070is, perception),—are agents which destroy sensation. Local Anæsthetics have been described (ante, page 402.) General Anæsthetics are certain volatile substances, mostly belonging to the class of alcohols and ethers, which when inhaled produce complete unconsciousness and loss of sensation (anæsthesia), with lessened motor power.

Narcotics also produce anästhesia, but the term is usually restricted to the effects of the volatile agents referred to, a full list of which may be found on pages 45 and 140. The principal members of this group areEther (Oxide of Ethyl).

Nitrous Oxide.
Chloroform.

Bromide of Ethyl.
Bichloride of Methylene.

Bichloride of Ethylene.

Antispasmodics (àyri, against, otaruós, a spasm),--are agents which prevent or allay spasm of voluntary or involuntary muscles in any portion of the organism. Some of the agents belonging to this class act by stimulation of the higher nervous centres, the

AGENTS ACTING ON ORGANS OF SPECIAL SENSE.

405

coördinating power, and the circulation, as Alcohol and Ether in small doses, Camphor, Musk, Valerian, etc. ; others by a depressant influence on the motor centres, as the Bromides; and still others by paralysis of the end-organs of the vaso-motor nerves, as Amyl Nitrite. A few depress all the vital functions, as Aconite, Tobacco, Lobelia, Hellebore, and Prussic Acid ; and a long list stimulate the bowels to expel gaseous accumulations, namely, Asafetida, Cajuput, Valerian, Musk, Aromatic Oils, etc. They are used in convulsive affections, especially asthma and other spasmodic diseases of the respiratory organs, hysteria, chorea, angina pectoris, epilepsy, etc. The principal antispasmodics are as follows, viz. Alcohol.

Aconite.

Ammoniac. Ether.

Lobelia.

Castor. Chloroform.

Tobacco.

Musk. Amyl Nitrite.

Hellebore.

Galbanum. Nitrites.

Opium.

Sumbul. Bromides.

Belladonna.

Ipecac. Potassium Iodide.

Stramonium.

Senega. Potassium Nitrate.

Hyoscyamus.

Silver Salts. Arsenic,

Prussic Acid.

Zinc Salts. Valerian.

Physostigma.

Copper Salts. Conium.

Curare.

Asafetida.

The Cerebellum is affected by a few drugs, their action upon its several lobes producing various disturbances of equilibrium.

Alcohol is the principal agent acting upon this portion of the brain, and different products of the still seem to affect different portions of the cerebellum. For instance, intoxication by wine or beer is said to cause lateral falling, that by whiskey an inclination to fall face downwards, cider a backward tendency (Brunton). Apomorphine in large doses produces a tendency to move in a circle, and therefore probably affects the cerebellum or the corpora quadrigemina.

AGENTS ACTING ON THE ORGANS OF SPECIAL SENSE.

Mydriatics (pódus, moisture),--are agents which produce dilatation of the pupil of the eye (mydriasis). Some act locally, others when given internally, and the principal ones (Atropine and its congeners) act both locally and internally, producing at the same time paralysis of the ciliary muscle resulting in temporary loss of accommodation, the eye remaining focussed for distant objects, and the intra-ocular tension being increased.

The dilating action of Atropine and its congeners is due to stimulation of the end-organs of the sympathetic nerve, increasing the power of the radiating muscular fibres of the iris, and also to paralysis of the end organs of the motor

oculi (3d cranial) nerve, lessening the power of the circular fibres or
sphincter iridis (see ante, page 96). When administered internally the drug
is carried by the circulation to the eye, acting thereon locally as if instilled
directly upon the conjunctiva. The principal mydriatics are those named in
the following list, viz.,-
Belladonna, Atropine.

Belladonnine (internally only).
Hyoscyamus, Hyoscyamine. Homatropine.
Stramonium, Daturine,

Gelsemine (locally only).
Duboisia, Duboisine.

Anästhetics (at last). Atropine, Duboisine and Homatropine are the mydriatics used by ophthalmologists.

Myotics (mów, to close), -are agents which produce contraction of the pupil. The alkaloid of Physostigma, Eserine, is the chief local myotic, and the only one used in ophthalmic practice. It acts by stimulating the circular muscular fibres of the iris, at the same time contracting the ciliary muscle so that the eye is accommodated for near objects only, and diminishes intra-ocular tension.

Muscarine, Pilocarpine and Nicotine are also local myotics, acting upon the end-organs of the oculo-motor nerve. Anæsthetics in the early stage of their action cause contraction of the pupil by lessening reflex action; later, when they begin to paralyze respiration the accumulation of venous blood irritates the centres and produces dilatation, which is a sign of failing respiratory power during anæsthesia. The myotic action of Opium is of central origin, probably the paralysis of the local reflex excitability. The chief myotics are as follows: Physostigma, Eserine.

Gelsemine (internally).
Opium, Morphine.

Lobeline (internally).
Pilocarpus, Pilocarpine.

Nicotine (locally).
Muscarine.

Anæsthetics (at first).

The Sensibility of the Eye is increased by Strychnine, the field of vision becoming extended, and the vision rendered more acute. If the drug be administered hypodermically the improvement will be more marked in the eye corresponding to the side of the body where the injection was made.

The sensibility for color is affected by drugs, Strychnine increasing the field for blue, Eserine diminishing it for red and green, and Santonin causing objects to appear at first of a violet and afterwards of a greenish-yellow color.

Visions are produced by several drugs, their action being probably on the cerebral sight-centres (angular gyrus and occipital lobes) rather than on the eye. Alcoholic delirium is a familiar instance, while Cannabis Indica often causes pleasant visions, and

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