0*9 



ASTRINGENTS. 



ASTRINGENTS. 



CoO 



ciple, but is owing to tannin, gallic acid, and hsematine, in vegetable 

 astringents, and is possessed by acids, and many metallic salts among 

 mineral agents ; and is also one of the effects of the application of cold 

 to the body. In vegetables, the astringent principles are found chiefly 

 in the bark (as oak), the root (as rhatany and tormentil), and the wood 

 (as logwood). As wood and bark form parts of exogenous trees only, it 

 is only from this section of the vegetable kingdom that any astringent 

 principles can be obtained. [See explanation of the term exogenous, 

 under the article AGE OF TREES.] Sir Humphry Davy found that the 

 inner layer of the bark possessed the greatest quantity of the astrin- 

 gent principle : this is the natural consequence of the mode in which 

 the sap descends from the leaves, namely, through this inner layer of 

 bark, whence it occasionally passes into the wood, which will then be 

 found to possess principles similar to those of the bark. Most astrin- 

 gent vegetables are red, owing to the presence of an acid in excess, 

 which is often manifest to the taste, as in rumex or sorrel. In 

 metallic astringents, when super-salts, the excess of acid is also very 

 perceptible to the taste, as in alum, which is a supersulphate of alumina 

 and potassa. 



The particular principle to which any substance is indebted for its 

 astringent power, may be ascertained by appropriate tests. When 

 tannin exists in plants, its presence may be proved by an insoluble pre- 

 cipitate taking place on the addition of a concentrated solution of 

 gelatin. The precipitate is a compound in definite proportions of 

 tannin and gelatin, being forty-six of tannin and fifty-four of 

 gelatin. Gelatin has therefore been proposed by Sir Humphry 

 Davy as a test of the quantity of tannin in different astringent 

 vegetables. (See 'Philosophical Transactions,' 1803.) But in the 

 practical application of this test there are some sources of fallacy 

 difficult to guard against. (See Papers by Dr. Bostock in Nicholson's 

 'Journal,' vol. xxiv. 1809, and by Mr. E. B. Stephens, in 'Annals of 

 Philosophy,' New Series, vol. x. p. 401.) Tannin rarely exists alone, 

 though it probably does so in catechu, but mostly along with gallic 

 acid. Extractive is also a frequent accompaniment of tannin, and is of 

 considerable service, assisting its action in the process of tanning. 

 Gallic acid strikes a bluish-black precipitate with all the salts of iron, 

 but a solution of the persulphate is the ordinary test. Hsematine 

 exists in logwood, along with tannin and extractive. It may be 

 known by combining with oxide of lead without undergoing any 

 change. 



The effect of astringents which is due to their chemical action is 

 nearly the same in dead as in living animal matter ; their long-con- 

 tinued application to the skin will produce a condition similar to that 

 of a tanned hide. They are therefore sometimes employed to effect 

 this, when internal parts are exposed, to change them from a secreting 

 to a non-secreting surface such as in irreducible prolapsed uterus. 

 Their use in this way however is very limited, whilst their vital action 

 is extensive and important. The chief effects of astringents are to con- 

 tract the muscular and vascular tissues, to diminish secretion, and 

 lessen irritability, and in many instances to impart strength or 

 increased tone to an organ or part. Their action is always greatest 

 on the part to which they are applied. When a drop of diluted acetic 

 or sulphuric acid is applied to the skin, whiteness of the part is 

 observed, which soon disappears, and the natural colour, or even a 

 more intensely red one, follows. If this is frequently repeated, the 

 structure of the part is changed ; it ceases to secrete, is no longer 

 pliant, but becomes stiff and inflexible. The loss of colour is owing to 

 the diminished calibre of the blood-vessels, which no longer admit the 

 red globule*. During the absence of these, the sensibility of the part 

 is lev than natural ; just aa cold and torpid fingers lose their fineness 

 of touch. Nearly similar effects may be supposed to follow the internal 

 administration of astringents, the action of which is greatest on the 

 intestinal canal, and less on parts remote from this ; yet it deserves to 

 be remarked, that as the intestinal canal is a mucous membrane, and 

 posncmce a muscular structure, parts of a similar structure are more 

 influenced by astringents introduced into the stomach than other parts 

 are : hence, increased secretion from the mucous membrane of the 

 lungs, or from the lining membrane of the bladder, or flow of blood 

 from arteries, is more effectually checked by astringents than increased 

 exhalation from serous surfaces. There is reason to believe that the 

 Mtringent principle of many plants does not enter into the circulation, 

 but passes along the whole course of the intestinal canal without being 

 absorbed ; for Sir Humphry Davy found, that when tannin is present 

 in grouses, as it is in that of aftermath crops, it is voided in the dung of 

 the animals which feed upon it. (See Davy, ' Elements of Agricultural 

 Chemistry, Appendix,' p. Ixi.) But that of other plants enters the 

 ytem so rapidly, that the astringency of the Ura Urti, or bear's 

 whortleberry, can be detected in the urine forty-five minutes after it 

 has been swallowed. In the case (d those which do not enter into the 

 circulation, any beneficial effect which they exert upon remote organs 

 must be attributed to that sympathy which exists in so great and 

 npquestionable a degree between the stomach and almost every organ 

 of the body. That such vegetable substances, while passing along the 

 intestinal canal, promote the fulfilment of its functions, is obvious, 

 from the effects following the use of food in which astringent principles 

 are absent. Plants possessing astringent powers and bitter principles, 

 uch as tormentil and the bog-bean, are very efficacious in preventing 

 the rot in sheep (as has beer already stated under ANTHELMINTICS), 



while watery grasses, among which no astringent plants grow, favour 

 the generation of worms. 



The primary sympathetic effect of several of the astringents which 

 ultimately enter into the circulation, is the most valuable in some of 

 the cases in which they are employed, such as dilute sulphuric acid, 

 which often checks haemorrhage by closing a bleeding vessel, before any 

 of it can be conceived to have been conveyed directly to the bleeding 

 orifice ; it checks the flow of blood iu the same way as cold suddenly 

 applied to the surface or skin does. The tonic effect of many 

 astringents, after their use for some time, first on the digestive organs, 

 and afterwards upon the whole system, and more especially upon any 

 weak organ, must be admitted, and borne in mind in forming our esti- 

 mate of their utility in a curative point of view. Without attempting 

 to account for the ultimate cause of the action of astringents, to do 

 which successfully seems impracticable in the present, imperfect state 

 of our knowledge, it may be stated, that under their influence a tension 

 of the parts is produced, during which the muscular and vascular struc- 

 tures acquire an increase of power, and secreting surfaces and glands 

 produce less fluid, but more natural secretions. Some indeed lessen 

 the action of the heart, and so stop the flow of blood from dilated or 

 ruptured vessels, such as the preparations of lead, which, though in 

 some degree astringent, ought to be considered at sedatives ; while 

 others which combine with, and neutralise the unhealthy or excessive 

 secretions, as lime and its carbonate with the secreted fluids of the 

 intestinal canal, are more properly termed absorbents than astringents. 

 When astringents are applied directly to the bleeding vessels, such as 

 to external wounds, or to the nostrils or gums, they are termed styptics, 

 and in such cases they often act chemically as well as vitally. 



Before proceeding to consider the cases in which astringents may 

 be advantageously used, an enumeration of the most common and 

 valuable substances may be given. Of vegetable astringents the chief 

 are barks, as of oak and willow, the best kind of the former of which is 

 obtained from the Quercus robur of Limueus (the true British oak) 

 which is synonymous with the Quercus pedunculata of Willdenow, while 

 the inferior sort is obtained from the Qufrcus sessijlora of Salisb., 

 which is synonymous with the Quercus robur of Willdenow. The best 

 willow-bark is procured from the Saiix pentandra, or sweet bay-leaved 

 willow, though very excellent bark is yielded by the Salijc Ruitelliana, 

 or Bedford willow. Roots, as of tormentil (Potentilla tormentitla); 

 bistort (Polyyonum bistorta) ; common avens (Oeam urbanum), which 

 are British plants ; and rhatany (Krameria triandra), rhubarb (Rheum 

 palmatum) ; pomegranate (Punica granatum), which are exotic plants ; 

 leaves of arctostaphylos ( Uva ursi), petals of the Sola yallica, fruits of 

 Prunus spinosa,or sloe-thorn (Punica granatum), and secreted juices of 

 many plants, as kino, from Petrocapus marsupium, and several others ; 

 catechu, from Acacia catechu, and galls, from Quercus infectoria ; in all 

 of which the astringent principle is tannin, with more or less of gallic 

 acid ; log-wood (ffamatoxylon Campechianttm), in which htematiue as 

 well as tannin possesses an astringent property ; and JEgle Marmelos, 

 or Indian Bad. Acetic acid must also be classed among the vegetable 

 astringents. 



The mineral astringents are diluted sulphuric acid, and salts of 

 iron, zinc, copper, silver, and the salts of lead. Cold, in whatever way 

 applied, is also a valuable astringent, particularly in the form of ice. 



In treating of the employment of astringents as curative agents, it is 

 necessary to distinguish between their action as local, direct, and often 

 chemical, and their action as general, influencing remote organs, their 

 effects upon which are vital rather than chemical ; also between their 

 mere astringent power and their tonic power. The beneficial effects of 

 many of the above-named astringents in checking increased secretion, 

 is doubtless often due to their tonic power ; for as in a weak state of 

 the system or any particular gland, the secretions are generally profuse 

 in quantity, a return to the healthy proportion and quality can only be 

 insured by increasing the power or tone of the body or gland, which 

 astringents do by bringing the living tissues into a closer or more 

 compact state, and which tonics do by heightening the vitality of the 

 debilitated structures. Hence astringents are beneficially employed in 

 diseases where a laxity of the muscular and vascular tissues exists, 

 accompanied with imperfect discharge of the functions of the secreting 

 organs. The stomach and intestinal canal being the channel by which 

 is conveyed the material necessary for the nourishment and vigour of 

 the system, and for maintaining a capacity to discharge their functions 

 in the other organs of the body, an impaired state of the structure and 

 functions of this canal extends to every other part. The re-establish- 

 ment of its healthy condition is a primary object in endeavouring to 

 cure many diseases. Of these intermittent and remittent fevers may be 

 taken as an example, since in these there is always great debility of the 

 digestive organs, and of all the parts which have the most intimate 

 sympathy with them, such as the skin. Astringents possessed of a 

 tonic power have, therefore, mostly been resorted to, in order to 

 remove this debility; cinchona-bark, willow-bark, and many others, 

 have been used with this intention. These, however, are to be avoided 

 whenever any acute inflammation exists, which must first be subdued 

 by appropriate means before tonic astringents can be safely or advan- 

 tageously used. In diseased states of the intestinal canal, hi which 

 greatly increased or unhealthy secretions take place, as diarrho?a, 

 dysentery, and cholera, the most careful inquiry should bo made into 

 the cause of the disease, that if it has its origin in an inflammatory 



