277 



COUCH GRASS. 



COUMARIN. 



278 



, 



for this work. Another estimate, made in 1857, was to the effect 

 that all the cotton worked up in Europe and America, excluding Asia 

 and Africa, would in 1856 have amounted to 1,795,000,000 Ibs. The 

 probable European consumption for 1859 is about 1,300,000,000 Ibs. 



The most trustworthy authorities on the subject of this article are 

 the same as those enumerated at the end of COTTON, CULTIVATION AND 

 SUPPLY. 



COUCH GRASS (Triticnm rcpens) is a common and most trouble- 

 some weed which infests arable land, especially that which is of a light 

 and mellow nature. It is perennial, and propagated both by seed and 

 by extension of the root, which is long and jointed; each joint pro- 

 duces a fresh shoot, which, in a favourable situation, soon becomes a 

 new parent plant, creeping along under the surface of the ground, and 

 spreading over a whole field with great rapidity. It appears above 

 ground like a blade of grass, or young wheat, which, in its tender 

 state, is readily eaten by sheep. A seed stem afterwards shoots up, 

 bearing a spike, composed of a middle rachis and alternate spikelets on 

 each side. Each of these produces three or four seeds, protected by a 

 long pointed chaff. Many of the seeds never come to perfection, owing 

 to the increase of the roots ; but in stiff ground and permanent pastures 

 the roots are prevented from spreading, and then the seeds ripen. The 

 principal propagation of the plant is by the root. The destruction 

 and extirpation of couch grass is one of the first things which an 

 experienced farmer sets himself to on taking occupation of land which 

 has been neglected by the preceding tenant. 



There is no law in this country which obliges a tenant to keep his 

 lands free from weeds. There is something of the kind in Belgium, 

 with respect to thistles and weeds which propagate by seed. An agri- 

 cultural code is necessary to protect the landlord, and to prevent the 

 woeful waste of labour produced by carelessness and bad manage- 

 ment; and until such a code is established by the good sense 

 and good feeling of neighbours, agriculture will never make rapid 

 progress. 



To extirpate couch grass a dry time must be chosen in summer ; the 

 land must be ploughed with a shallow furrow, to bring the roots to the 

 surface ; when the land is dry, it must be rolled to break the clods, 

 and all the roots which lie near the surface must be gathered by the 

 harrows or the couch rake. Sometimes the roots are matted into 

 tufts, which can only be got up by means of a fork or prong. In this 

 case no manual labour should be spared, especial care being taken not 

 to break the roots, but to get them out whole, with all their offsets, if 

 possible. After this, Finlayson's harrow may be used on light lands ; 

 or an instrument of a similar nature, called in Scotland a ijmbber, 

 which will bring up all the roots that are within six or eight inches of 

 the surface. When all the couch has been apparently eradicated, there 

 will still remain a sufficient number of pieces and joints, broken off by 

 the instruments and left in the ground, to produce a fresh crop of 

 couch grass, especially if the land is frequently stirred, and showers 

 intervene. Hence the vulgar notion that some lands breed couch, and 

 that it is useless labour to be at much expense to eradicate it. In very 

 heavy land, couch grass is easily kept down if an opportunity be taken 

 to plough it to the surface in dry weather. The stiff clods in which 

 the root* are entangled contract in drying, and in contracting destroy 

 the texture of the root ; when they crumble after a shower, the couch 

 may be collected by hand, and burnt or carried away. 



When a quantity of the roots of couch grass has been collected, they 

 are usually burnt in heaps on the ground ; the ashes serve to enrich 

 the land in some degree. The curious in such matters do, however, 

 assert that a much more profitable use may lie made of them. When 

 they are cleaned from the earth which adheres to them, they are found 

 to be nutritious and farinaceous. Pigs eat them greedily ; horses and 

 cows will also eat them, especially when boiled or steamed ; and weight 

 for weight they contain not much less nutritious matter than potatoes. 

 By maceration and washing, a good fecula is obtained, which, with hot 

 water, forms a jelly-like arrow-root. The decoction of the root has 

 been recommended as a cooling and demulcent beverage, and not 

 without apparent reason ; but if it be not thought worth while to wash 

 and steam the couch for food, it is still more profitable to decompose 

 it by means of lime than to burn it. For this purpose it should be 

 gathered into a large heap and watered to induce fermentation. When it 

 has heated, it should be turned over and mixed with quick lime in a con- 

 siderable proportion ; after two or three turnings with the spade, with 

 an interval of a few weeks, it will be found converted into rich mould, 

 which may then be spread over the land, either as a top-dressing for 

 clover and artificial grasses, or ploughed in with the seed, where this 

 method is practised. 



To keep the land free from couch grass occasional summer tillage is 

 necessary, which may be given when turnips are sown, or after an 

 early crop, such as tares cut green, Trefolium tnearnatum, or winter 

 barley, without losing a crop. In a well-managed farm, couch grass 

 nlinnld no more appear than docks or thistles. In Belgium a slovenly 

 farmer in called a couch grass farmer. 



< eat the blade of couch grass from instinct to purge and vomit, 



'. lias been named, in French, chim-dent, or d<xfs touth ; but 



the ihape of the young shoots from the root may also probably have 



led to that name, for they have a great resemblance to a canine 



tooth. 



It haa been doubted whether, in some situations, couch grass might 



not be cultivated to advantage for its roots ; no experiments, however, 

 have been made in cultivating this prolific plant, as far as we know ; 

 but it is not unworthy the attention of those who take a pleasure in 

 increasing the resources of agriculture. In years of great scarcity, the 

 root of couch grass has been used in northern countries, mixed with 

 flour, in making bread. It contains nothing unwholesome, and has a 

 considerable resemblance in taste to the potato. The water in which 

 the root of couch grass has been boiled may be used in the manufacture 

 of bread ; it would probably add considerably to the weight of the 

 loaf when baked, but may perhaps communicate an unpleasant taste 

 to it. 



COUCHING. [CATARACT.] 



COUGH, a violent expulsion of air from the lungs, attended, when 

 the act of coughing recurs in rapid succession, that is, when there is a 

 fit of coughing, with correspondingly rapid inspirations. Cough is a 

 violent and sonorous expiration, during the effort of which a much 

 greater quantity of air is expelled from the lungs than is returned by 

 the corresponding act of inspiration. 



The mouth, nose, fauces, pharynx, larynx, trachea, and bronchi, arc 

 lined by a highly irritable and exquisitely sensible membrane. That 

 portion of this membrane which lines the air passages, properly so 

 called, namely the larynx, trachea, and bronchi, possesses the properties 

 of irritability and sensibility in so great a degree, that it cannot endure 

 without the most violent excitement the slightest contact of a foreign 

 body. It is necessary to the due performance of the function of the 

 lung, one of the most important of the organic circle, that the tubes 

 which lead to it should always be perfectly unobstructed ; should in- 

 variably present to the air a free and uninterrupted passage. Among 

 the expedients adopted to secure this purpose, one of the most impor- 

 tant consists in the disposal and action of the membrane which lines 

 the internal surface of the air-tubes. This membrane abounds with 

 blood-vessels and nerves, by the action of which a large quantity of 

 water is constantly separated from the blood, by which the tubes are 

 kept in a state of perfect suppleness and moisture. A layer of the 

 thick, tenacious, and viscid substance, called mucus, also separated 

 from the blood by this membrane, is spread over its entire surface, by 

 which it is defended from the irritating properties of the air, with 

 which it must always be in contact. Moreover, the heat generated by 

 the process of secretion warms the air in its passage to the lungs ; and 

 so great is the degree of heat communicated to the air during its pro- 

 gress, that before it reacBes the lung it is brought to the same tempe- 

 rature as that of the blood. Accordingly when the lining membrane 

 of the air passages is sound, when the temperature of the air ranges 

 within a certain limit, and when the air is pure, holding in solution or 

 suspension a foreign and noxious body, the external cold exciting air 

 passes deep into the interior of the body, into the very centre of the 

 chest, not only without occasioning irritation, but even without pro- 

 ducing sufficient sensation to induce consciousness. But when either 

 of these conditions is changed, the state natural to the respiratory 

 process is disturbed ; irritation is excited ; warning is given that some 

 danger threatens the system ; and an effort is made to remove the 

 offending cause. The warning is announced, and an effort is made to 

 remove the danger, by the act of coughing. [CATARRH ; BRONCHITIS ; 

 PHTHISIS ; LUNGS, DISEASES or ; CROUP.] 



COUMARIC ACID. [COUMARIN.] 



COUMARIN (Cj-HjOJ. An odoriferous crystalline principle found 

 in the Tonka bean (Coa.murov.na odorata, or Dipterix odorata), in the 

 common Melilot (Melilotut offieinalit), in Woodruff (Asperitla, odorata), 

 and in the sweet-scented Vernal Grass (Antkoxanthum odoratum), to 

 which the scent of hay is owing. 



To prepare coumarin, coarsely powdered tonka beans are digested 

 for several hours in hot alcohol of 80 per cent. After nitration, the 

 greater part of the alcohol is recovered by distillation, and when the 

 residue begins to appear turbid, water is added, by which means the 

 coumarin is precipitated in a more or less crystalline state. It may be 

 obtained pure ami colourless by treating with animal charcoal, and re- 

 crystallisation from alcohol. 



Coumarin crystallises in rectangular plates. It melts when heated 

 to 122, and at 518 boils, and sublimes without decomposition. It 

 baa an agreeable aromatic odour and a burning taste, is but slightly 

 soluble in cold water, freely so in boiling water or dilute acids. 

 Chlorine, bromine, and iodine act upon it, and yield crystalline 

 compounds. 



Nitrofoumarin (C,jH 5 (NO,)OJ, containing an equivalent of NO, in 

 the place of an equivalent of hydrogen, is formed when coumarin is 

 gradually added to cold fuming nitric acid ; dilution with water causes 

 the nitrocoumarin to precipitate in snow-white flocks. Hot nitric acid 

 converts it into picric acid. 



Nitrocoumarin crystallises from solution in alcohol in white silky 

 needles. It melts at 338", at a higher temperature sublimes without 

 decomposition, and condenses in pearly crystals. 



Coumaric acid (C 18 H,O ) is produced when coumarin is boiled in 

 strong solution of potash. Upon diluting with water and adding 

 excess of hydrochloric acid, it is precipitated in the form of lustrous 

 transparent plates. 



Coumaric acid is colourless. It has a bitter taste. It is soluble in 

 alcohol, ether, and water. It melts at 374, and at a higher tempe- 

 rature sublimes, but with partial decomposition. Fused with hydrate 



