KEY AND INDEX 



in just the reverse manner from the "step-up" transformer. See 

 "Step-up" and "Step-down" Transformers, Vol. VI, p. 198. 



Transmutation of Species. The change of species in the 

 process of evolution. Jean Baptiste de Lamarck (see Vol. IV, 

 p. 150), early in the nineteenth century, called attention to this 

 fact, and thus laid one of the foundation-stones to Darwin's 

 theory of evolution. For a full treatment of the subject, see 

 "Theories of Organic Evolution," Vol. IV, p. 140. 



Treadmill. An implement for producing power, in which an 

 animal or man by walking up a movable inclined plane trans- 

 mits power. The animal, although continually walking, remains 

 in the same spot, the platform receding at a rate corresponding 

 to the walking rate of the animal. See Vol. VI, p. 60. 



Trichina Spiralis. A parasite found in pork (and several of 

 the lower animals), which may be transferred to the human 

 system through the channel of the alimentary canal, and set up 

 a severe and often fatal disease known as trichinosis. The 

 parasite was discovered by James Paget, then a medical student, 

 in 1833. See Vol. IV, p. 207. 



Trichinosis. See "Trichina Spiralis." 



Trophic Centers. Waller discovered that every nerve fiber, 

 sensory or motor, has a nerve cell to or from which it leads, 

 which dominates its nutrition, so that it can only retain its 

 vitality while its connection with that cell is intact. Such cells 

 he named trophic centers. See "Functions of the Nerves," Vol. 

 IV, p. 249- 



Tungsten Lamp. An incandescent electric lamp in which the 

 filament is made of the metal tungsten (or some alloy) in place 

 of the usual carbon filament. See "The Tungsten Lamp," Vol. 

 VI, p. 234- 



Turbine Engine. A steam engine in which the action of steam 

 upon a shaft causes it to revolve, thus producing directly rotary 

 motion. In the ordinary reciprocating engine the power has to 

 be transformed into rotary motion by the intervention of a 

 crank. See "Turbine Engines," Vol. VI, p. 124. 



Turbine Water-wheels. A horizontal water-wheel made to 

 revolve by the escape of water through orifices, under pressure 

 derived from a waterfall. Probably the most powerful water 

 turbines are those at Niagara Falls. See "Niagara in Harness," 

 Vol. VI, p. 183; and "Running Water," Vol. VI, p. 70. 



[51] 



