Tachy. Denoting swift or accelerated.

Tachycardia. An increase in heart rate above the normal rate.

Tactile. Of touch. T. corpuscle. Receptor end-organ of touch.

Tadpole. The larva of an amphibian or of sea squirts.

Tangoreceptor or tactor. A receptor sensitive to slight pressure differences.

Taanins. Group of astringent substances of wide occurrence in plants, dissolved in cell-sap; particularly common in the bark of trees, unripe fruits, leaves, and galls. Complex organic compounds containing phenols, hydroxy acids, or glucosides.

Tapeworm. Parasitic flatworm (Cestoda). Adult lives in gut of vertebrates; body long and ribbon-like, consisting of a chain of proglottides, attached to host by scolex. Eggs develop into six-hooked embryos (onchosphereres) which pass out with faeces of host. If eaten by suitable animal, develop into larval stage. This becomes sexually mature only when eaten by the definitive host, which may not occur until after it has parasitized another host.

Target cell. Any cell that responds to specific hormones.