80

ELEMENTS OF MATERIA MEDICA.

Polygonacece; and to these may be added kino. These agents are prin-cipally remarkable for causing local contraction and corrugation (or 'astriction) of the tissues. They contract and give greater density to )muscular fibres ; dimmish the calibre of the blood-vessels and exhalents, ‘and thereby check haemorrhage (whence their denomination of styptics), iand diminish secretion and exhalation when applied to mucous membranesor other secreting surfaces. In the mouth they give rise to a peculiarsensation of roughness and stypticity. Some writers have ascribed these {effects to a physical or chemical agency. Thus Dr. Cullen places ;astringents among substances acting on the simple solids, though, in fanother part of his treatise, he admits that they act on the living, as wellas on the simple solids. The late Dr. Adair Craw lord (An ExperimentalInquiry into the Effects of Tonics, § c., 1816 ) ascribed the effects of bothastringents and bitters to their influence in promoting the cohesion of theanimal fibre. He immersed some pieces of intestines, of skin, &c., invarious bitter and astringent infusions, while others were placed in water,merely as a standard; and he then observed the comparative weightsrequired to break them, from which he inferred the relative strength ofdifferent tonics. But this mode of reasoning naturally leads to erroneousinferences, since the vital powers of the system are quite overlooked.The relaxed state of parts, which astringents are useful in obviating,depends not on a mere mechanical or chemical alteration, but in somechange in the state of vital powers; and, therefore, the agents which 'counteract it, must have some other than a mere physical action. ]Moreover, the results obtained by Dr. Crawford depended probably on 1the different degrees of antiseptic power possessed by the substances femployed. Astringents produce the constitutional effects of the bitter |tonics: administered in moderate doses, they promote the appetite, !assist digestion, and increase the tone and vigour of the general lsystem. They are capable of fulfilling the same therapeutic indicationsas the bitter tonics. Thus they have the power of preventing the (occurrence of a paroxysm of intermittent fever, and in cases of debilityare often useful, independently of their power of checking debili-tating discharges. But this group is principally employed for its localeffects; to obviate relaxation of fibres and tissues, and to prevent orcheck excessive discharges. ;

c. The third group contains those vegetable tonics which possess j

both bitterness and astringency in an eminent degree; it may, therefore, 1be denominated astringent bitters. It includes cinchona bark, from Gin - •chonacece; spigelia, from Spiyeliacea; elm-bark, from Ulmacece; andwillow-bark, from Salicacece. It combines the effects of both bitters andastringents, and is by far the most important group of the class, since it Icontains cinchona bark, the most powerful of the vegetable tonics. |

d. The fourth group contains the aromatic bitters, which possess f

bitterness, with an aromatic flavour (derived from the presence of volatile foil), and, in some cases, astringency likewise. This group contains ?wormwood and elecampane, from the order Composite ; cascarilla, from |Euphorbiacee,; angustura bark, from Rutacecc; and hops, from Urticacece. iThey possess the combined properties of aromatics and bitter tonics, and |are, therefore, useful where these are indicated. I

e. The fifth group contains the acid tonics-, namely, the mineral |acids, to which, perhaps, may be added alum. These, taken in the |