A derivative of Atropia. Its action is similar to that of atropia, though weaker.

It is used only in ophthalmic practice, its advantage being, that whilst it acts as promptly though not so energetically as atropia, its effects subside in about one-fourth the time.

Tabaci Folia- Leaf Tobacco. - The dried leaves of Virginian Tobacco, Nicotiana tabacum. Cultivated in America.

Characters. - Large mottled-brown ovate or lanceolate acuminate leaves, bearing numerous short glandular hairs; having a peculiar heavy odour and nauseous-bitter acrid taste; yielding, when distilled with solution of potash, an alkaline fluid, which has the peculiar odour of nicotin, and. precipitates with perchloride of platinum and tincture of galls. Not manufactured.

Composition.-Tobacco contains a most powerful alkaloid, nicotin. and a concrete volatile oil, nicotianin, as well as alkaline salts and other less important substances. Nicotin, C10H14N2, is a colourless oily-looking fluid, with an irritating odour of tobacco, and an acrid taste. It forms salts with acids, which, like nicotin itself, are readily soluble in water.

Tobacco smoke contains the very smallest trace only of nicotin, or none, but a number of volatile bodies, chiefly pyridin compounds, such as pyridin, C5H5N; picolin, C6H7N; lutidin, C7H9N; collidin, C8H11N, which have somewhat the same action as nicotin, but less severe. Hydrocyanic and hydro-sulphurous acids, other simpler gases, creasote, etc., also occur in tobacco smoke.

Preparation. Enema Tabaci.-20 gr. infused in 8 fl.oz. of Boiling Water for one enema.

Action And Uses. 1. Immediate Local Action And Uses

Tobacco, taken by the mouth, is a gastro-intestinal irritant, causing salivation, nausea, vomiting, severe colic, and repeated evacuations. The same effects may follow tobacco smoking, and the application of the leaf to the unbroken skin, or of snuff to the nose. Tobacco smoking and snuffing may thus cause catarrh of the throat and stomach, and promote the movement of the bowels-facts of therapeutical interest. Tobacco is never given by the mouth. Snuff is an errhine.

Injected into the rectum, the Enema rapidly produces peristaltic movements, with expulsion of gas and faeces, and the specific effects now to be described. It has been used in ileus and constipation.

2. Action In The Blood

Nicotin very rapidly enters the blood from all surfaces, but does not directly affect the corpuscles.

3. Specific Action And Uses

All the organs are quickly reached by nicotin. It acts chiefly upon the nervous structures, which it first stimula tes, if given in very minute doses ; but afterwards depresses in an extreme degree, causing Intense and universal debility, which, with the local irritation of the alimentary canal, constitute a condition of collapse. On analysis, it is found that tobacco causes pleasing cerebral excitement; decided stimulation of the motor centres in the cord, with a feeling, and true increase, of muscular strength (ending in convulsions and paralysis, in poisonous doses); excitation, followed by paralysis, of the peripheral nerves, both sensory and motor; but no direct effect on the muscles. Respiration is first excited, then disturbed, and finally arrested, death by tobacco being due to arrest of the centre. The action of tobacco on the heart is, contrary to general belief, not directly the cause of death: it is first slowed, then accelerated, and finally weakened with slowing, but it beats after respiratory death. The blood pressure falls, rises, and falls again, with the cardiac action, and. from direct central and peripheral effect on the vasor apparatus. The temperature falls.

Tobacco was formerly employed in enema to produce general muscular debility and relaxation, for the reduction of hernia ; but chloroform has entirely displaced it. Its depressant effects suggest its use as an antispasmodic in whooping-cough, asthma, hiccup, tetanus and strychnia poisoning, rigidity of the cervix uteri, etc., but such a powerful drug is very seldom employed.

4. Remote Local Action And Uses

Nicotin is excreted unchanged in the urine, saliva, and faeces. As a diuretic, it was formerly given in dropsy, but this use of the drug has been abandoned.