LEAVEN. 



LEECHES. 



170 



20,000,000^. Most of the leather made in this kingdom, and of the 

 articles formed with it, are used at home. The importations of hides, 

 skins, and articles of leather in 1859 were as follow : 



Hides, untanned, dry . * . 



wet . 

 tanned, tawed, or dressed . 



Leather boots and shoes . 

 Leather gloves . . 



. 250,296 cwt. 

 . 611,391 



. 4,962,192 Ibs. 



. 713,274 pairs 

 . 4,590,201 



The actual number of hides and skins imported for conversion into 

 leather is not stated in the official returns ; but persons in the trade 

 estimated them a few years ago as follows : 



Hides and kips 

 Calf skins 

 Horse hides 

 Seal skins 

 Goat skins . 

 Sheep skins . 

 Lamh skins 

 Kid skins 

 Deer skins . 



2,550,000 



270,000 



230,000 



590,000 



460,000 



210,000 



1,430,000 



50,000 



90,000 





The exports of leather, except manufactured articles, are very small : 

 they amounted only to 42,136 cwt. in 1859. The leather goods 

 (excluding saddlery) exported were 6,669,210 Ibs., with a declared 

 value of 1,359,189/., or about 4. per Ib. on an average. The saddlery 

 and harness were estimated only by value, 289.631/. The Australian 

 colonies are the great purchasers of all these articles. 



LEAVEN. [BREAD.] 



LECANORIC ACID. [LicHEXs, COLOURING MATTERS OF.] 



LECANORIN. [LICHENS, COLOURING MATTERS OF.] 



LEDITAXX1C ACID. [TANNIC ACID.] 



LEECHES, MEDICAL USE OF. Of the species described in the 

 article AKNELIDA, in NAT. HIST. Div., it is intended to treat here only 

 of those of the genus Sanguisuga (Savigny), or Jatrobdclla (Blainville), 

 as they only can be employed for medical purposes. The same reason 

 induces us to confine our attention to the species S. ojKcinalii (Savigny) 

 and S. medii.-inali iSavigny). 



Though the S. oltscura and S. interrupta might be employed to with- 

 draw blood, yet the S. ojicinalis and S. medicinalis are chiefly so used. 

 The former is also termed the Hungarian or green leech (Hirudo pro- 

 Hi, of Carena ; S. meridional!*, of Risco), while the latter is termed 

 the German, or brown, or gray leech, also the true English or specked 

 leech. The one species abounds in the south of Europe, while the 

 other is a native of the north. The S. vudicinnlii is now rare in 

 England, owing to the draining of so many of the ponds and bogs in 

 which it formerly abounded. The same is nearly the case in France, 

 which used to be supplied chiefly from the district of La Brenne, 

 but now from the frontiers of Russia and Turkey. England derives the 

 immense number required mostly from Sweden, Poland, and Hungary. 



The genus Sanyuituya is characterised by having the body elongated, 

 the back convex, the belly flat, and the oral and caudal extremities 

 narrowed, before they spread out into discs or suckers. The body 

 consists of from ninety to one hundred or more soft rings, which do 

 not increase in number, but only in size, with the age of the animal 

 which requires about eight years to come to maturity ; and if it escape 

 being devoured by others which prey upon it, it may attain twenty 

 years. The anterior or oral extremity is rather narrower than the 

 caudal : it is provided with ten blackish points or eyes, and a triradiate 

 (not triangular) mouth, furnished with three cartilaginous jaws, each 

 armed with numerous cutting-teeth. The anus is very small, situate 

 on the dorsal surface of the last ring. 



The .S'. ufficinalii has a green body or light blackish-green, the back 

 marked with six longitudinal bands of an iron colour, spotted with 

 black spots at their middle portion and edge. The belly is of a yellowish 

 green mthout spott, but broadly bordered with black. The segments 

 nf the body are very smooth. It i large, often seven inches long. I 

 lives in pools and rivers. There are three varieties. 



S. medicinal has the body of a deep green, its back marked with 

 six longitudinal bands of an iron colour, pretty clear, spotted' with 

 black points, generally triangular. The belly is greenish, spotted 

 and broadly bordered with black, and the segments of the body 

 rough from granular eminences. It inhabits ponds and small lakes. 



O,f the anatomy of the leech it is not necessary to say much. Thi 

 skin consists of two layers, the external or epidermis, and thi 

 internal or corium. The first is transparent, resembling a serou 

 membrane ; this is thrown off from the body every four or fivi 

 days. The corium consists of condensed cellular tissue. It displayi 

 the divisions into rings, and in it resides the colouring matter of the 



The alimentary system consists of the mouth, the stomach, salivarj 

 glands, liver, and anus. The mouth has a triradiate figure, formed o 

 three equidistant lines, meeting in a centre, about the middle of th 

 oral disc. Inside are three sublenticular jaws or piercers, white, am 

 of a cartilaginous appearance. On the free, curved, sharp margin o 

 each jaw there are about sixty small fine-pointed teeth. The alimentary 

 canal consists of an oesophagus, a long stomach, with ccccal sacs, an ' 



n intestine. The oesophagus is a muscular tube, and commences 

 etween the inner angle of the three jaws by a roundish opening : 

 t dilates as it approaches the stomach, but at its termination it con- 

 racts into a circular aperture : the whole length does not exceed a 

 juarter of an inch. The stomach occupies two-thirds of the length of 

 he animal, and is formed of eleven compartments or cells. Each of 

 hese divisions, that is, from the second to the eleventh, gives off on 

 ach side a sac, of which those of the last cell are much the largest. 

 ?he intestine is about an inch in length ; at the upper orifice is a 

 valve, and at its lower a sphincter. These organs can contain nearly 

 lalf an ounce of blood ; so that there is nothing remarkable in the 

 tatement that leeches have been known to exist three years in water, 

 without any other nourishment than they could obtain from it ; for the 

 >lood is received into cells quite distinct, in the first eight of which it 

 remains for months, without undergoing any change either in colour 

 or fluidity : over these cells the animal has a perfect control, merely 

 allowing so much nutriment to pass into the alimentary canal as is 

 necessary to preserve its existence. This accounts for the reluctance 

 t the animal, after being used to abstract blood, to repeat the opera- 

 tion ; it not only being gorged at the time, but provided with 

 nutriment sufficient to serve it during almost a sixth portion of its 

 life. In its native abode the true medicinal leech does not seem to 

 ake any solid aliment, but subsists on the fluids of fish, frogs, &c. 



Leeches are oviparous. The ova remain in the uterus for some 

 ;ime, where they become invested first with a serous membrane, and 

 then with a glutinous fluid, which remains attached to them after 

 their expulsion, and serves as a protecting covering after they are 

 deposited in the clay and holes bf the sides of the ponds. The leeches 

 jenerally deposit the cocoaiw from May to the end of September. It 

 would seem that these animals do not multiply in great abundance 

 unless they have tasted blood, particularly that of cows. On this 

 account the leech-dealers of Bretagne drive horses and cows into 

 the ponds to such an extent that the cattle of the district are in 

 general wretched-looking, and the leech-gatherers not much better. 



About five years are required before the leech attains a state of 

 maturity ; while very young they are quite unfit for medical purposes. 

 They are caught in various ways, by the hand, or by a person wading 

 in the shallow waters during the spring of the year, when they adhere 

 to his naked legs ; but in summer, as they have retired to deeper 

 waters, a raft is constructed of twigs and rushes, by which a few are 

 entangled. Baits are deposited, generally pieces of decayed animal 

 matter or liver, to which the leeches resort, and are then caught ; but 

 this last method is thought to injure the health of the animal. 

 Many sicken and die on the journey, especially during warm 

 weather. They are conveyed either in bags or small barrels with a 

 canvas cover. 



Leeches are subject to many diseases, several of which are epidemic, 

 and spread in the troughs with great rapidity. On the first appearance 

 of illness the sick should be immediately separated from the healthy. 

 Care should be at all times taken that different species of leeches be 

 not associated in the same trough, for they prey upon each other. The 

 Ilcemopgit vorax, and H. nigra (Pieudobdella, Blainv.), or common black 

 leech, devour greedily the S. medicinalis or S. rutyaris, though they 

 cannot penetrate the skin of vertebrated animals. The horse-leech, 

 Ilamopia ianyuisodea, Sav. (the Hirudo sanguisi/ga, Linn.; Hypubdella, 

 Blainv.), is not certainly without the power of penetrating the human 

 skin, though the black leech, often confounded with it, has no such 

 power, from want of teeth. 



A leech may be known to be in good health if it be active in the 

 water and plump when taken out. In Prussia leeches are divided into 

 three classes, according to their weight : the first not exceeding 30 

 grains ; the second weighing between 30 and 60 grains; the third from 

 60 to 90. Leeches above 90 grains are not to be used, unless specially 

 ordered. In each prescription the physician is required to state what 

 description of leech he intends should be used. In the case of children 

 such regulations are highly proper, as an excess of blood abstracted 

 may easily produce serious and often fatal consequences. Leeches vary 

 in the quantity they can abstract, from one drachm to half an ounce : 

 from one to two drachms is the average. The quantity is often doubled 

 by the expedients resorted to after the leech has been removed, either 

 dry or wet clothes being applied, or in many cases cupping-glasses, but 

 cataplasms of linseed-meal are most beneficial where they can be 

 applied. 



One gray or German leech is deemed equivalent to two green or 

 Hungarian leeches. The cases requiring or justifying the application 

 of leeches are stated under the respective diseases, and need not be 

 repeated here. It is of more importance to indicate the proper mode 

 of applying them. The leech, though not so accurate an index of the 

 weather as is commonly believed, is yet sensible of atmospheric changes, 

 and in some (probably peculiarly electric) conditions of the atmosphere 

 cannot be induced to bite. In such cases time ought not to be wasted, 

 nor the patient exposed injuriously or kept in a fatiguing position, but 

 some other mode of blood-letting should be had recourse to. More- 

 over, if the leech bo sickly, it can rarely be made to bite. Certain 

 states of the patient also hinder or indispose them to bite. Where the 

 skin is very thick they cannot puncture it ; or if the person has been 

 using sulphur, the exhalation of the sulphuretted hydrogen is disagree- 

 able to them ; even the fumes of tobacco, vinegar, &c., will prevent 



