THERAPEUTICS. 209 THERMO-CHEMISTBY. stated by Cusliny: (1) Organic substances which ar<' characterized chiefly by their local action, such as pepper, mustard, and turpentine. (2) Organic substances characterized chielly by their action after absorption, such as alcohol, strych- nine, and morphine. (3) The alkalies, alkaline earths, acids, and allied bodies. Under this head are grouped the various salts of ammonia, etc. There is a gradual transition from this group to (4) the heavy metals, as silver, gold, iron, etc. Another class ( 5 ) embraces ferments, secretions, and toxalbuniins. thus consisting of a number of substances which are either present in the normal bod}' or are merely substitutes for nor- mal secretions. In the last group (6) menstrua and mechanical remedies are found, preparations which are used only for their mechanical effects, and which, while they are included in the Pharmacopa?ia, are not for the most part drugs. THERE'SA, Saint. See Teresa. THEKESINA, ta're-ze'na, or THEREZINA. The capital town of the State of Piauhy, Brazil, on the right bank of the river Paranahiba, 230 miles from the city of that name at its mouth (Map: Brazil, J 5). The town is regular in construction, but uninteresting and unhealthful. Population, about 6500. THERESIOPEL, tara'ze-o'p'l; or Maeia- TnERESioPEL (Hung. Szabadka) . A royal free city of the County of Bacs, Hungary, 109 miies by rail south -southeast of Budapest (Map: Hungary. F 3 ) . It is a scattered town, lying in a great, rich plain between the Danube and the Theiss, and has noteworthy churches. Theresi- opel is the centre of a fine large corn-raising district, which also produces tobacco. The manu- factures include linens and shoes. The town has a fine trade in grain, wine, horses, cattle, hogs, hides, and wool. Population, jn 1890. 73,526: in inOO, 82,122, chiefly Catholic Magyars and Serbs. THER'IDI'ID-ffi (Neo-Lat. nom. pi., from Gk. ffepiSiov, tlicridion, diminutive of 6-fip, thcr, wild beast). A family of spiders known as the cobweb-weavers. These are small spiders with very slim legs, and include most of the familiar house spiders. They are generally soft and of a light color, with the abdomen large and round and the legs lacking in spines. The eyes are all of about the same size and are placed in two rows across the front of the head. The mandibles are weak and without teeth at the end. The maxillae are pointed at the end and turn inward toward each other. The family is one of the largest of the order Arachnida. Many species of Theridiidae spin their webs in the fields on bushes. The web is a flat or curved sheet, sup- ported by threads which run in many directions, under which the spider hangs head dowmward. The egg cocoons are round and soft and hang in the web. THE'BIODON'TA (Neo-Lat. nom. pi., from Gk. d-qpiov, thrrion, diminutive of d-qp, thfr. wild beast + 6So6t, odoim. tooth). A suborder of ex- tinct Permian and Triassic reptiles, the skulls of which show remarkable resemblance to those primitive carnivorous mammals. See Cyno- GNATHUS; ThEROJIGRPIIA ; REPTILE. THE'RIOSTI'CHUS (Neo-Lat., from Gk. Brjplov, ihf-rinn. diminutive oidiip, Iher. wild beast + (Touxos, sQuchos, crocodile). An extinct croco- dile with body less than two feet long, skeletons of which are found in the Purbcck beds of the English Upper Jurassic. See Crocodile ; Teleo- SAURUS. THERMAL SPRING (from Gk. eippcT/, tltcniit', heat, from tiep/iit, thermos, hot). A spring whose temperature is higher than the average temperature of the locality in which it emerges. The temperature may vary therefore from a minimum of a few degrees above the freez- ing point, which, however, is limited to thermal springs in high altitudes or great elevations, to a maximum represented by the boiling point of water under the local conditions. When the tem- perature reaches the latter limit the flow of the spring may take the form of periodical eruptions; a thermal spring of this character being known as a geyser (q.v.). The higher temperature of thermal springs as compared with ordinary springs ma.y be caused bj- volcanic agencies or by the circulation of the waters at gi-eat depths in the earth's crust previous to emergence. The liottest springs are usuall.v found in volcanic re- gions, and their high temperature is due to com- ing in contact with uncooled lava, which when buried at some depth retains its heat for a long time. It seems probable, also, that some springs are heated by gaseous emanations from Uie earth's interior, or, indeed, receive material con- tributions from that source. Thermal springs are quite common, however, in districts that have been free from volcanic disturbances, at least since remote geological times. The increase in temperature under such conditions can best be explained by peculiarities of geological structure which permit the surface waters to descend to great depths when they are heated and thence are returned to the surface under the influence of hydrostatic pressure. See Spring. THERMES, tarm (Fr., from Lat. thermce, warm baths). The only remains of the Roman palace which occupied the site of the present HStel de Cluny, Paris. The ruins are those of the great baths connected with the palace, and include a frigidarium 65 feet long and 59 feet high, still uninjured, although up to 1820 it had long borne the weight of a garden laid out over it. The ships' prows of the vaulting are said to be the origin of the arms of Paris. A collection of Roman antiquities discovered in Paris is pre- served in the hall. THERMIC FEVER. See He.it-Stroke. THERMIDOR, Fr. pron. tar'me'd5r' (Fr., from Gk. Bipp-ri, therme, heat + Swpoy, doron, gift). The eleventh month in the French revolu- tionary calendar. It extended from .July 19th to August 18th in the years I.-VII. and from .lulv 20th to August 19th in" the years VIII.-XIII. The 9th Thermidor of the year II. (.July 27, 1794) is historically memorable as the date of Robe- spierre's fall and the termination of the Reign of Terror. The name Thermidorians was given to all those who took part in this coup d'etat, but more particularly to those who were desirous of restoring the monarchy. See French Revoh'- TiON ; Robespierre. THERMO-CHEMISTRY. The branch of general chemistry that deals with the thermal phenomena accompanying chemical transforma- tions. While those phenomena are caused partly by the chemical changes proper, they may be
