408 PRINCIPLES OF ANIMAL BIOLOGY 



Thorax {tho' raks). A middle portion of the body of many animals, between head and 

 abdomen. 



Thricozoa (thrik' o zo' a). A class of animals (hair animals) in Oken's early classifica- 

 tion. It comprised the mammals which Oken also called Ophthalmozoa. 



Thymus {thi' mus). A ductless gland located near the gill clefts, or in the neck, or in 

 the anterior part of the thorax in various vertebrates. 



Thyroid (ihi' roid). A ductless gland located in the ventral part of the pharynx. 



Thysanoptera {ihi' sa nop' ter a). An order of insects of small size, commonly living 

 in flowers or otherwise concealed on plants. 



Tibia (Hb' i a). The innei* one of the two bones in the lower leg of vertebrates except 



the fishes. 

 Tibio-fibula (lib' i o fib' u la). The fused tibia and fibula of some Amphibia. . 



Tibio-tarsus {lib' i o tar' sus). A compound bone in the leg of a bird, formed of the 

 tibia and certain of the tarsal bones. 



Tissue {tish' u). A group of cells of similar structure forming a continuous mass or 

 layer. 



Tonsil {ton' sil). A glandular organ at the side of the throat. 



Tonus {to' nus). A state of continuous activity, as in muscle. 



Trachea {tra' ke a) . The tube conveying air to and from the lungs in vertebrates. 

 Also an air tube in insects and some other invertebrates. 



Tradescantia {tra' des kan' shi a) . A genus of plants including the spiderwort and 

 wandering jew. 



Transverse process {trans vers' pros' ess). One of a pair of projections at the sides 

 of a vertebra in most vertebrate animals. 



Trematoda {trem' a to' da). A class of Platyhelminthes, parasitic flatworms with 



suckers and without cilia. 

 Triassic {tri as' sik). Of the earliest Mesozoic time. 

 Triaxon {triaks' on). Having three axes diverging from a common point; said of 



sponge spicules. 

 Triceratops {tri ser' a tops) . A genus of three-horned dinosaurs of late Cretaceous 



time in western North America. 



Trichinella {trik' i net' la). A genus of parasitic roundworms, the cause of the disease 



trichinosis. 

 Trilophodon {tri lo' fo don). An extinct genus of animals from the Miocene of several 



continents; probably an ancestor of the elephants. 



Trimerotropis maritima {trim' er of ro pis ma ril' i ma). The beach grass-hopper. 



Trionychidoe {tri' o nik' i dee). A family of turtles. 



Tripalmitin {tri pal' mi tin). A fat composed of glycerol and three molecules of pal- 

 mitic acid; the most abundant fat in man. 



Triploblastic {trip' lo bias' tik). Composed of three fundamental layers of cells. 

 Triton {tri' ton). A genus of salamanders. 

 Tropism {tro' piz'm) . A response of an organism to a stimulus. 

 Trypsin {trip' sin). A proteolytic enzyme produced by the pancreas. 

 Trypsinogen {trip sin' ojen). The inactive substance from which the enzyme trypsin 

 is produced. 



Tryptic {trip' tik). Of the nature of trypsin; said of proteolytic enzymes that act in an 

 alkaline medium. 



