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TOOLS AND MACHINEBY 435 TOOTH manufacturers (1914) shows 601 estab- lishments devoted to the manufacture of agricultural implements of all kinds. These employed 58,118 persons; had a capital of $838,531,673; paid salaries and wages amounting to $47,603,790; and produced goods valued at $164,068,835, The export of agricultural implements from this country to foreign countries is of importance and is steadily growing. In 1890 the value of agricultural imple- ments from the United States was $3,- 859,184. By 1900 it had increased to $16,099,149. It then remained stationary for the next two years, increasing slowly until 1905, when it amounted to $20,721,- 741. In 1910 it had reached $28,124,033. In the last year previous to the World War (1913) it reached the large sum of $40,572,352. The effect of the World War was especially noticeable in the agricultural implement industry. In 1914 the exports had fallen to about $32,000,000, and in 1915 to $10,300,000, a figure lower than any since 1898. A slight improvement was shown in 1916, with total exports of over $17,600,000; these rose, in 1917, to over $26,500,000; in 1918 to over $35,000,000; and in 1919 to $41,195,494, the highest total yet achieved. This, however, was exceeded in 1920, when the exports of agricultural implements were valued at $46,277,269. TOOMBS, ROBEE.T, an American statesman; born in Wilkes co., Ga., July 2, 1810; was graduated at Union College, Ky., studied law at the University of Virginia; was a Whig member of Con- gress from Georgia in 1845-1853; and a United States Senator in 1853-1861. He was expelled from the Senate in 1861, and in the same year was elected to the Confederate Congress and also became Confederate Secretary of State. He re- signed to become a Brigadier-General in the Confederate army. After the war he resided abroad till 1867. He refused to take the oath of allegiance to the United States Government, being to the end of his life bitterly opposed to the recon- struction policy of the government. He died in Washington, Ga., Dec. 15, 1885. TOOTH, one of the hard bodies in the mouth, attached to the skeleton, but not forming part of it, and developed from the dermis or true skin. True teeth consist of one, two, or more tissues, differing in their chemical composition and in their microscopical appearances. Dentine, which forms the body of the tooth, and "cement," which forms its outer crust, are always pres- ent, the third tissue, the "enamel," when present, being situated between the den- tine and cement. The dentine, which is divided by Owen into hard or true den- tine, vaso-dentine, and osteo-dentine, con- sists of an organized animal basis, dis- posed in the form of extremely minute tubes and cells, and of earthy particles. The tubes and cells contain, besides the calcareous particles, a colorless fluid, which is probably transuded blood plas- ma, or liquor sanguinis, and contributes to the nutrition of the dentine. In hard ^6-8 I8-20 12.-15 2.0 FIRST TEETH The figures refer to months after birth or true dentine the dentinal tubes pro- ceed from the hollow of the tooth known as the pulp cavity, in a slightly wavy course, nearly at right angles to the outer surface. When a part of the primi- tive vascular pulp from which the den- tine is developed remains permanently uncalcified, red blood is carried by "vas- cular canals" into the substance of the tissue. Such dentine is called vaso-den- tine, and is often combined with true den- tine in the same tooth, as, for example, in the large incisors of certain rodents, the tusks of the elephant, and the molars of the extinct megatherium. When the cellular basis is arranged in concentric layers around the vascular canals and contains "radiated cells," like those of bone, this is termed osteo-dentine ; resem- bles true bone very closely. The cement always corresponds in texture with the osseous tissue of the same animal, and wherever it occurs in sufficient thickness, as on the teeth of the horse or ox, it is traversed like bone by vascular ca- nals. The enamel is the hardest of all the animal tissues, and contains no less than 96.4 per cent, of earthy matter (mainly phosphate of lime), while dentine con- tains only 72 per cent, and cement and ordinary bone only 69 per cent, of earthy matter. In a few fishes the teeth consist of a single tissue — a very hard kind of non- vascular dentine. Teeth consisting of dentine and vaso-dentine are very com-