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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.
Musk. Amyl Nitrite.
Пресас. Potassium Iodide.
Senega. Potassium Nitrate.
Silver Salts. Arsenic.
Zinc Salts. Valerian,
Copper Salts. Conium.
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 (róðos, 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
Belladonnine (internally only).
Gelsemine (locally only). .
Anæsthetics (at last). Atropine, Duboisine and Homatropine are the mydriatics used by ophthal. mologists.
Myotics (wów, 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. Anästhetics 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,
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 Sodium Salicylate in some persons produces very disagreeable ones. Digitalis may produce subjective sensations of the continued presence of light.
Amblyopia, or impairment of vision from nerve-changes, is produced temporarily by Quinine, and may be permanently induced by Tobacco, Alcohol, Lead and Urea.
The Ear is affected by several drugs. Strychnine and Opium increase the excitability of the auditory nerve or of the centre for hearing (superior temporo-sphenoidal convolution), and make that faculty much more acute. Quinine and Salicylates produce hyperæmia of the auditory apparatus, causing subjective noises, as humming, buzzing or ringing, which are very unpleasant. Hydrobromic Acid and the Bromides, also Ergot, will diminish the congestion and to a great extent will neutralize or prevent these noises.
Quinine in large doses is believed by some to have produced permanent injury of the sight and the hearing, but authentic cases of such action are extremely rare, if indeed they can be found at all. Temporary deafness is osten caused by Quinine, but it usually disappears soon after the administration of the drug is stopped.
The Sense of Smell is also increased by Strychnine, and decreased by all cerebral depressants and by those which produce changes in the nasal mụcous membrane, e.g., Potassium Iodide.
The cerebral centre for this faculty is situated at the tip of the temporosphenoidal lobe, and the terminal branches of the olfactory nerve are distributed upon the mucous lining of the upper portion of the nasal fossæ. Strychnine probably stimulates the former, and all drugs acting upon the latter region would have more or less effect upon the power of distinguishing smells.
The Taste is not much affected by drugs except as each makes its peculiar impression on the nerves of taste, and may overcome that of another agent. Smell has much to do with taste in many instances, the expedient of holding the nose while swallowing Castor Oil being familiar to everyone.
The“after-taste" of drugs is often different to their original taste; thus Bitters are said to leave a sweet aster-taste, and the same is claimed for Quinine if given in acid solution so as to be entirely dissolved, and if washed out of the mouth with water immediately after swallowing. Substances which are excreted from the system in the saliva (as lodides) leave a very persistent after-taste.
AGENTS ACTING ON RESPIRATION.
The Respiratory Centre is situated in the medulla oblongata, close to the termination of the calamus scriptorius. It probably consists of thoracic and diaphragmatic Inspiratory centres, the act of expiration being considered normally a passive one, due to the natural contraction of the walls of the air-vesicles, and the return of the diaphragm and thoracic walls to the position from which they were moved by the inspiratory effort. An Expiratory Centre must also exist for the initiation of forced expiration, as in the production of voice, cough, sneezing, etc. The chief Inspiratory Nerves are the pulmonary branches of the vagus. The Expiratory Nerves are the nasal branches of the fifth, the superior and inferior laryngeal, and the cutaneous nerves of the chest and abdomen.
Respiratory Stimulants increase the activity of the respiratory centre, quickening and deepening the respirations. Such agents areHeat. Brucine.
Digitalis. Quebracho. Strychnine. Thebaine.
Zinc salts. Tobacco (briefly). Atropine. Apomorphine. Copper salts. Alcohol i briefly). Duboisine. Emetine.
Ammonia. Ether (briefly). Strychnine also stimulates the vagus tract. Electricity applied to the nervetrunks or to the inspiratory muscles, is a direct respiratory stimulant. Veratrine, Eserine and Muscarine stimulate the vagus terminations, quickening the respiration, but afterwards slow it by depressing the respiratory centre. Aconite stimulates the end-organs of the vagus when given in small doses.
Respiratory Depressants lower the activity of the respiratory centre, rendering the respirations slow and shallow. The chief agents of this class areCold. Gelsemium. Alcohol.
Saponine. Camphor. The last ten named first excite the centre for a brief period and then de. press it.
Errhines and Sternutatories (lv, in, pev, the nose; sternuto, to sneeze),-are agents which produce increased nasal secretion and sneezing, when locally applied to the mucous membrane of the nose. The first term is usually applied to substances which
cause increase of the mucus without sneezing, the latter to those which invariably produce sneezing. The drugs should be in powder for application. The stimulus produced by these agents is transmitted by the nasal branches of the fifth nerve to the respiratory centre, exciting the sudden and forcible expiratory effort called sneezing ; also to the vaso-motor centre, contracting the smaller vessels throughout the body and producing a general rise in the blood-pressure. The principal agents of this class areTobacco, as snuff.
Pulmonary Sedatives diminish cough and dyspnoea by lessening the irritability of the respiratory centre or the nerves of respiration. Some act by directly depressing the respiratory centre, as those enumerated under the preceding head; others by removing some irritant from the passages, or by lessening local congestion, as the expectorant group; and others by lowering the excitability of the vagus end-organs in the lungs, and that of the other afferent nerve filaments in the respiratory tract.
Opium has the most powerful influence as a sedative to the respiratory centre, and mucilaginous or saccharine substances soothe the local irritation, hence the latter are so frequently used as vehicles for the former in coughmixtures. Hydrocyanic Acid has a similar sedative action, hence the use in coughs of Prunus Virginiana and other substances containing it. Belladonna stimulates the respiratory centre, but at the same lessens the excitability of the vagus terminations in the lungs, and completely arrests secretion from the bronchi. Stramonium acts similarly. The principal pulmonary sedatives may be enumerated as follows, viz.Opium. Prussic Acid.
Turpentine. Belladonna. Amyl Nitrite.
Expectorants (ex, out of, pectus, the breast), -are remedies which modify the secretion of the broncho-pulmonary mucous membrane, and promote its expulsion. They may be divided into
Nauseating Expectorants,-in large doses act mechanically by expelling the mucus in the act of vomiting, in small doses by