PHYSIOLOGICAL CLASSES OF MEDICINES.

67

substances of this group are valuable in certain painful affections of thealimentary canal (of the stomach especially) unaccompanied by inflam-mation.

d. The fourth group includes those cerebro-spinants which occasionsleep or stupefaction, and, when given in large quantities, apoplexy.They are the narcotics properly so called. The most important is opium,to which perhaps may be added henbane and lactucarium. In smalldoses they frequently cause excitement; in larger ones they diminishthe contractility of the muscular fibre, or even occasion actual paralysis,lessen the sensibility of the body generally, and give rise to sleep orstupor. The apoplectic condition caused by the use of poisonous dosesof opium has been denominated narcotism. In this state the pupils areusually contracted. The uses of this group may be inferred from itseffects. In small doses opium is employed as a stimulant: in largerdoses opium, henbane, and lactucarium, are employed to relieve pain, inwhich case they are denominated anodynes (from a, privitive , and oCvvt),pain) or paregorics (from Trapiryopiu, to soothe or alleviate ) ; they are alsoused to diminish inordinate muscular contraction (convulsion or spasm)when they are termed antispasmodics; and, lastly, to procure sleep, whenthey are called hypnotics (vttvo-umc, from 5 irvog, sleep) or soporifics (fromsopor, a deep sleep, and facio, I make.)

e. The fifth group is closely allied to the fourth, from which perhapsit ought not to be separated. It includes those agents which causeinebriation, followed by sleep and stupefaction, and, when large doseshave been swallowed, apoplexy. This group, therefore, lias beendenominated inebriants or intoxicants. It contains alcohol, wine, andether. These agents arc remarkable for their great exciting properties,as well as for the peculiar delirium which they occasion, by both ofwhich effects they are principally distinguished from the precedinggroup, lly long-continued use, alcohol occasions the disease termeddelirium tremens, and which is characterized by wakefulness, delirium,and tremor. Inebriants are used in medicine on account of theirstimulant qualities.

Musk, valerian, and some other substances usually denominatednervines, though closely related to this group, may with more proprietybe noticed under the head of stimulants.

f. The sixth group is a provisional one to contain belladonna andperhaps stramonium, the mode of operation of both of which substancesis less perfectly understood than of some of the before-mentioned medica-ments. The first of these causes dilatation of the pupil, obscm-ity ofvision, dryness of the throat, difficult or impossible deglutition, aphoniaor difficulty of articulation, faintings, and delirium, followed by sopor orlethargy: convulsions are rare. Laennec {Dr. Forbes's Translation, p. 77,1827) says that it relieves dyspnoea by diminishing the necessity forrespiration. In a case related by my friend Dr. T. Davies ( Lectureson Diseases of the Lungs and Heart , p. 496) a plaster of belladonnaapplied to the abraded skin cured a severe form of angina pectoris.Oculists employ belladonna to dilate the pupil.

g. The seventh group includes tobacco and foxglove, both of which areremarkable for their depressing influence on the circulating organs, inconsequence of which they are denominated sedatives. When takeninternally, in large doses, they give rise to nausea, vomiting, giddiness,