Appendix 839 



Ionization, breaking up of solute molecules into electrically charged ions in the 



process of solution. 

 Ions (i' ons) (Gr. ion, going), electrically charged particles into which molecules 



may be split when in water. 

 Iris (i' ris) (L. iris, rainbow), colored part of eye. 

 Irritability (ir i ta -bil' i ti) (L. irrito, excite), ability to receive and respond to 



external or internal stimuli. 

 Ischium (is' ki um) (Gr. ischion, hip), posterior and dorsal bone of the pelvic 



girdle. 

 Islands of Langerhans, areas in the pancreas which secrete the hormone insulin. 

 Isogametes (i so ga -mete') (Gr. isos, equal; gamete), similar gametes (sex cells). 

 Isogamy (i-sog'ami), union of similar gametes (contrast with Heterogamy). 

 Isolation (is o la' shun) (L. isolate, island), to keep away from; in heredity the 



prevention of interbreeding between certain organisms. 

 Isotonic solution (iso-ton'ik) (Gr. isos, equal; tonikos, tension), one with 



osmotic pressure equal to that of protoplasm. 



Jejunum (je -joo' num) (L. jejunus, empty), middle or second part of the small 



intestine between the duodenum and ileum. 

 Jellyfish, group of jellylike coelenterates. 

 Jugular (jug' u lar) (L. jugulum, collarbone), pertaining to the neck, as jugular 



vein in neck. 



K 



Kappa particle, a "killer" particle in a Paramecium. 



Karyokinesis (kar i o ki -ne' sis) (Gr. karyon, nut; kiriein, to move), see Mitosis. 



Karyolymph (kar'iolimf) (Gr. karyon, nut or nucleus; L. lympha, liquid), 



liquid ground substance of the cell nucleus. 

 Karyosome (kar'iosom) (Gr. karyon, nut or nucleus; soma, body), nucleus-like 



body in the cell nucleus as opposed to the nucleolus (plasmosome). 

 Keratin (ker' a tin) (Gr. keras, horny), insoluble substance, similar to chitin, 



forming the basis for horns, hoofs, etc. 

 Kinetic energy (ki -net' ik) (Gr. kineo, move), possessed by virtue of motion such 



as falling water, winds, etc. (contrast with Potential energy). 

 Krause's membrane, transverse membranes^ within striated, voluntary muscle. 



Labial (la'bial) (L. labium, lip), pertaining to lip. 



Labium (la' bi um) (L. labium, lip), lower lip of insects. 



Labruni (la' brum) (L. labrum, lip), upper or anterior lip of insects, etc. 



Lactase (lak' tase) (L. lac, milk; ase, enzyme), enzyme that changes lactose 



(milk sugar) into dextrose and galactose. 

 Lacteals (lak' te al) (L. lacteus, milky), lymphatic vessels of small intestine to 



convey the milky chyle from the intestine through the mesenteric glands 



to the thoracic duct. 

 Lacuna (la -ku' na) (L. lacuna, cavity), cavity in which cells are located, as in 



bone, cartilage, etc. 



