KS 



THYMUS GLAND. 



T1LIA. 



tho it arum wulgare of older botauUU, and at one time had some 

 reputation as ao en-bine. 



Til V.\l I'S r.l.ANI > (which in the calf and lamb is called the Sweet- 

 bread), i> an ciyon situated behind the sternum, in the anterior 

 mediastinum, in front of the pericardium and the large vessels arising 

 from the base of the heart. In the embryo and the infint it ho*, in 

 proportion to the rest of the body, a very considerable size ; in after- 

 life it beoomei comparatively smaller, and at last nearly disappear!!. 

 It is of an elongated form, its greatest dimension being from above 

 downwards, and is composed of two chief portions, which by careful 

 dissection may be separated in the middle line. At each end it bean 

 two processes, or horns, of which the upper are longer and more 

 slender than the lower, and the right are usually longer than the left. 

 It is supplied by several branches from the internal mammary, inferior 

 thyroid, and mediastinal arteries, to which veins of considerable size 

 correspond. Its absorbent vessels are numerous and large, but not 

 more so than in other glands of equal vascularity. 



The Thymus Gland is composed of a great number of similar small 

 manes or lobules, which may be separated by dissection, and are 

 held together by fine cellular tissue continued from that which invests 

 the whole gland. The lobules vary in size from half a line to three 

 lines in diameter, and have simple or complex cavities filled with a 

 milky fluid. Sir Astley Cooper ('The Anatomy of the Thymus 

 Uland ') says that the lobules are arranged in spiral lines, so that the 

 gland may be unravelled into a sort of knotted rope of lobules, which 

 are wound around a central cavity or reservoir, with which the cavities 

 of the lobules communicate. But the existence of such a central cavity 

 is not generally admitted. 



The fluid contained in the cells of the Thymus Qland is, in young 

 and healthy animals, opaque and creamy. It has been particularly 

 examined by Mr. Gulliver (Appendix to Gorber's ' General Anatomy '), 

 who has found that both in its chemical composition, and in the 

 abundance and structure of the globules which it contains, it closely 

 resembles the fluid of the lymphatic glands. 



Of the function of the Thymus Gland scarcely anything probable is 

 known. Whatever it be, it is performed most actively during foetal 

 life and the first year of extra-uterine life ; for during this time the 

 Thymus Gland grows at the same rate as the rest of the body, its cells 

 are full of fluid, and the fluid is thick and abundant in globules. 

 From the end of the first to the end of the third year its size does not 

 materially vary, but after this time it gradually diminishes, and after 

 the twelfth or fourteenth year it is rare to meet with more than a 

 alight trace of it 



THVNNTS. [ScoilBRlDA] 



THYONE.S, or THYONID/E, a family of Echinodtrmata, belonging 

 to the order Jlolothuriadir. They are characterised by the pyriform 

 shape of their bodies whilst resting, and a cylindrical form whilst 

 moving; they are contractile, and covered all over with numerous 

 papillose suckers; they have 10 branching tentacles. From their 

 elongated character, and their body being covered with suckers, they 

 resemble some forms of Oaclui, and have hence been called Sea- 

 Cactuses. The genus J/vlotliuria is often included in this family. It 

 is distinguished from Tliyonc by possessing 20 tentacles, which are not 

 branched as in Thyone. 



Thyone is thus characterised : Body nearly regular, covered with 

 scattered wart-like suckers; tentacles 10; teeth long and thread-like. 

 There are three British species of this genus. 



T. papillon, the Common Thyone, has an elongate-ovate body of a 

 brownish-white colour, with the tentacula much pinnated. It was 

 lint found by Dr. Johnston, and has since been taken several times on 

 the British coooto. 



T. Portloctu and T. Kaphanut are the remaining British species. 



TUYROID QLAND if an organ situated in the middle and fore 

 part of the neck, in front and by the sides of the thyroid cartilage of 

 the larynx (from which it baa its name), and of the cricoid cartilage 

 and the upper part of thu trachea [LARYNX], to which it is closely 

 fixed by cellular tissue. It is composed of two chief lateral portions 

 or lobe*, and a smaller portion or isthmus connecting them. A fourth 

 portion, which is long and slender, and is named the middle column 

 or horn, usually pa-sea upwards from the isthmus in front of the 

 larynx. The lateral lobes are of a somewhat pyramidal form, about 

 two inches long, and an inch wide at their bases. The whole gland 

 u proportionally larger in the embryo than in the adult, and in 

 women than in men. 



Of the function of this gland but little u known. It is subject to 

 enlargement in scrofulous states of the system, and this disease is 

 known by the names of lironchocele and Goitre. 



THYS.\XIII>ACTYLI;.S. [IMI-AMD.B.] 



Til Y.SAXOPOUA. [STOMAPODA.] 



THYSANU'RA, Apterous Insects, with six legs and peculiar organs 

 of motion on their sides, or at the extremity of the abdomen. They 

 undergo no metamorphosis. They have been grouped by Latreille 

 under two families, of which itpitma and Podura, two Linnacan 

 genera, are the respective types. In the first we have a number of 

 brilliant silvery little insect*, covered with small scales, which are used 

 as tests for the powcn of microscope glasses. They have long setaceous 

 many-pointed antenna:, distinct palpi to the mouth, and moveable false 

 feet on the aides of the abdomen ; the body is terminated by orticu. 



lated sete, three of which are especially conspicuous. The Podurcllir 

 have 4-pointed antenuio, indistinct palpi, an abdomen terminated by 

 a forked tail, which in folded under the belly when the animal is at 

 rest, and serves to aid it in leaping. They are little, long, ."oft 

 insect*. The Lepumeiut and Podunllat live chiefly among wood or 

 under stones. 



TIARA. [VOLUTID*.] 



TIA1US. [DKACONINA.] 



'HAULS, a genus of PrinyMida. 



TIBIA. [SKELETON.] 



TIBIANA, a genus of Polypiariit. 



TICHODKOMA. [CERTHIAD.B.] 



TICKS. [AcARiD.t ; TRACUEARIA.] 



TICO'REA, a genus of Plants belonging to the natural order liutacetc. 

 It has a small 5-toothed calyx, a uionopetalous funnel-shaped corolla 

 with a long tube, and a 5-cleft limb, either equal or unequal. The 

 stamens are from five to eight, of which from two to six are often sterile. 

 The disc is cup-shaped, surrounding the ovary ; the stigma 5-lobed. 



T. jaiminijlora is a shrub from 7 to 8 feet high, a native of Rio 

 Janeiro. The leaves are tcruate aud stalked ; the leaflets lanceolate, 

 from 1 to 6 inches long, tapering to the base, acuminate, obtuse, deep 

 green with pellucid dots. The calyx is rather downy, the corolla 

 white, downy, glandular, with pellucid dots. A decoction of the leaves 

 is drunk by the Brazilians as a cure for framboeaia. 



T.febrifuga differs but little in its character from the last species, 

 but in its stm being generally arborescent, its panicles contracted, its 

 flowers not more tlnn half the size, the bracts more numerous and 

 foliaceoua, and the style more protruded. The bark is intensely 

 bitter, astringent, and is regarded as a febrifuge. 



(Lindley, Plan Mcdica.) 



TIQA. [PiciD-E,] 



TIGER. [FEMD.e.1 



TIGER-BITTERN. 



TIGER-CAT. [FEUD*.] 



TIGLIUM. [CROTCH.] 



TIGRIS. [FELID.JS.] 



TIQRISOMA, Mr. Swainson's name for the Tiger-Bitterns. Tho 

 species have the bill as in A rdta ; face, and sometimes the chin, naked ; 

 legs almost feathered to the knees ; inner toe rather shorter than the 

 outer ; claws short, stout, regularly curved ; anterior scales reticulate 

 or hexagonal. Mr. Swainson considers this to be the rasorial type, 

 and he arranges it as a sub-genus of the family Ardeadus, between Butor 

 (Antiq.) and Xycliardea. 



TILESIA. [MlLLETORID*.] 



TILGATE BEDS. A portion of the great series of strata in tho 

 Weald of Kent and Sussex, interposed between the green-sands and 

 the Portland oolite, is thus named by Dr. Mantel), who bos described 

 the numerous and interesting organic remains which it contains. 

 (Mantel), FouiU of tlte British Museum.) 



TI'LIA, a genus of Plants belonging to the natural order Tiliacar. 

 The trees in England are called Lime-Trees, in Swedish Linn, and in 

 German and Dutch Linden. They are characterised by possessing a 

 5 parted deciduous calyx ; 5 petals ; numerous free or somewhat poly- 

 adelphous stamens; a globose, villous, 1-styled, 5-celled ovary. All 

 the species are handsome trees, with alternate, heart-shaped, acute, 

 serrated, deciduous leaves, and fragrant yellowish panicled flowers. 

 The wood is light, smooth, and white, and the sap possesses a consi- 

 derable quantity of sugar. They arc principally natives of Europe 

 and America. 



T. Eafopam, the European or Common Lime-Tree, has petals without 

 scales, and cordate acuminate serrated leaves, which are smooth, with 

 the exception of a tuft of hair at the origin of the veins beneath, and 

 are twice the length of the petioles ; the cymes are many-flowered, 

 and the fruit is coriaceous and downy. This tree is abundant in the 

 middle and north of Europe. It is very common in Great Britain, 

 although some doubts have been expressed as to its being truly indi- 

 genous. It is however admitted into all BritUh Floras; and there 

 can be no doubt, from its wide diffusion, that it is truly naturalised 

 in this country. It was well known to the ancients, and is spoken of 

 by both Theophrastus ami Pliny. It is a very general favourite in 

 Europe, and is planted in public places, parks, and approaches to 

 resiliences, in France, Germany, Holland, and Great Britain. For this 

 purpose its large size, handiouie appearance, and profusion of sweet 

 flowers well adapt it. The wood is in considerable request. Thu 

 Russian mats used by gardeners and upholsterer* are made from its 

 bark. The flower* secrete a large quantity of nectar, and exhale a 

 delicious scent. The seed of the lime possesses a large quantity of 

 albumen, which i nutritious and perfectly innocuous. 



The Lime-Tree attains a great sge; and many specimens, celebrated 

 for their age and size, exist Tho principal street of Berlin is called 

 Uuter den Linden, from the lime trees which are planted on each side. 



Many varieties of this tre > are described ; and, as is usual in these 

 cases, some authors have elevated them to tho rank and importance of 

 species. 



T. microphylla, the Small-Leaved Lime, has its petals without 

 nectaries or scales; cordate, roundish, acuminated, serrated leaves, 

 smooth above and glaucous beneath, with scattered as well as axillary 

 hairy blotches, and compouud many-flowered umbels. This is identical 



