A text-book of pharmacology and therapeutics; or, The action of drugs in health and disease, . rawn down it at once returnsto its original position, and the frog still attempts to escape when itis aroused. Fibrillary contractions are observed in many of the later, the reflexes disappear, the muscles become flaccid,and eventually complete paralysis occurs from a peripheral, curara-likeaction. Nicotine has but little toxic action on the lowest invertebrates, butas the nervous system begins to be difterentiated it causes paralysis,and still higher in the scale the paralytic actio
A text-book of pharmacology and therapeutics; or, The action of drugs in health and disease, . rawn down it at once returnsto its original position, and the frog still attempts to escape when itis aroused. Fibrillary contractions are observed in many of the later, the reflexes disappear, the muscles become flaccid,and eventually complete paralysis occurs from a peripheral, curara-likeaction. Nicotine has but little toxic action on the lowest invertebrates, butas the nervous system begins to be difterentiated it causes paralysis,and still higher in the scale the paralytic action is preceded by a stageof stimulation. Circulation.—The action on the circulation is extremely complex,as a number of factors are involved. After moderate quantities the20 306 SUBSTANCES ACTlSd AFTER ABSORPTION heart is slow and nia\- stand still in diastole for a few seconds, butthen recovers gratkially and regains its former rhythm or becomessomewhat quicker. The slow pulse is due to stimulation of the gangliaon the vagus nerve (Fig. 24, N), exactly the same efiects being pro- Fig. 24. Diagram of the regulating nerves of the heart. P, inhibitory cranial autonomicfibres (vaRus), terminating around ganglion cells in the auricle (..4). The axis cylindersissuing from these cells terminate on the muscular fibres of the auricle and ventricle (, accelerator sympathetic fibres terminating around ganglion cells in the stellate gang-lion G. The axis fibres of these ganglion cells run through the Annulus Vieussenii andterminate on the muscular fibres of the auricle and ventricle. A^ N points at whichnicotine, coniine, curarine, etc., act—the ganglion cells surrounded by the terminationsof the nerves. M, points at which muscarine and atropine act—the terminations of thefibres which arise from the intra-cardiac ganglia on the cranial autonomic path. E, pointsat which adrenaline acts—the myoneural junction on the sympathetic path. duced as by stimulation of the vagus fibres in
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