THORAX

(Yunanca köken — orijinale bakınız.) The second segment of insects is so called by Latreille and Andouin; the term is restricted to the upper surface of the tnmk by Linne and Fabric i us. In Arachnidans the thorax and head are confluent, and form but one segment, which is termed the cephalotborax. As a cavity appropriated to the reception of the circulating and respiratory organs, the thorax is only distinct in Mammals. Thorax. The chest; the part of the body between the neck and the abdomen. It contains the heart and lungs, the oesophagus, the thymus gland, the thoracic duct, part of the aorta and vena cava, the vena azygos, the eighth pair of nerves, and a part of the great intercostal nerve. Thorax. In Grecian Antiquities, a piece of defensive armour consisting of two parts, one defending the back, and the other the belly; called lorica by the Romans. The more ancient were made of padded linen; but they were also made of leather, bra , iron, and other metals. THORl' NA. (From Thor,the Scand in avian deity.) An earthy substance discovered, in 1828, by Berzelius in a. rare Norwegian mineral called thorite, which is a hydrated silicate of thorina. Like the other earths, thorina is the oxide of a heavy grey metal, which has been termed thorium, and which is not acted upon by water; but when heated in the air it burns with great brilliancy into a white oxide. Thorina obtained in this way is white, infusible, and very heavy, its specific gravity being 9-4. It is insoluble in all acids except sulphuric, and in that with difficulty. Its equivalent is about 68. Thorina is distinguished from alumina and glucina by its insolubility in caustic potash, and from zirconia by being precipitated by ferrocvanuret of pota ium. [s. 1246]