838 Appendix 



Incus (ing' kus) (L. incus, anvil), middle or anvil bone of the ear of certain 



vertebrates. 

 Indusium (indu'sium) (L. indusium, cover), membranous cover of a fern sorus. 

 Infection (in -fek' shun) (L. in, in; facere, to make), invasion of tissues by patho- 

 genic organisms with a resulting pathologic condition. 

 Infundibulum (in fun -dib' u lum) (L. infundere, pour into), funnel-like outgrowth 



from the ventral part of the diencephalon of. the brain (see Pituitary 



gland). 

 Infusoria (in fu -sor' i a) (L. infusus, crowded in), class of Protozoa very common 



in hay infusions, on plants in water, etc. 

 Ingest (in -jest') (L. ingestus, take in) take in food. 



Inhalant (in -hal' ant) (L. in, in; halere, breathe), to draw in or inspire. 

 Inheritance, transmission of traits from one generation to another. 

 Inhibitor (in -hib' i ter) (L. in, in; haheo, to have), restrain or check. 

 Inner cell mass, the inner group of cells of the embryonic morula in contrast to 



the outer layer or trophectoderm (trophoderm). 

 Innominate (in -nom' i nat) (L. in, not; nomen, name), nameless. 

 Inorganic (in or -gan' ik) (L. in, not; organic), not organic but pertaining to 



nonliving. 

 Insecta (in -sek' ta) (L. insectus, cut into), class of Arthropoda to which insects 



belong. 

 Insectivorous (in sek -tiv' or us) (L. insectus, insect; voro, to eat), insect eating. 

 Insertion (in -sur' shun) (L. insertus, join), place of attachment, as the more 



movable end of a muscle (contrast with Origin). 

 Instinct (in' stingkt) (L. instinguere, to incite), subconscious fixed reflex act due 



to a definite arrangement of an inherited pattern of nerve cells and tissues. 

 Insulin (in' su lin) (L. insula, island), hormone secreted by the islands of Langer- 



hans of the pancreas. v 



Integument (in -teg' u ment) (L. integumentum, covering), covering or investing 



layer. 

 Intercellular (in ter -sel' u lar) (L. inter, between; cellula, cells), between cells. 

 Internal receptor, sense organ within the body. 

 Internal respiration, passage of oxygen from the blood into the protoplasm of 



tissue cells (contrast with External respiration). 

 Internal secretion, see Hormone or Endocrine. 

 Internode (in' ter node) (L. inter, between; nodus, knot), space between two 



joints. 

 Intestine (in -tes' tine) (L. intestinus, internal), part of the digestive tract be- 

 yond the stomach. 

 Intracellular (in tra -scl' u ler) (L. intra, within; cellula, cells), within cells (con- 

 trast with Intercellular). 

 Intussusception (in tus su -sep' shun) (L. intus, within; suscipere, take up), growth 



by adding new materials within the living protoplasm (contrast with 



Accretion). 

 Invaginate (in -vaj' i nat) (L. in, in; vagina, sheath), to fold in, as in the gastrula. 

 Invertebrate (in -vur' te brat) (L. in, not; vertehratus, vertebra), lower animals 



without vertebrae or notochord (contrast with Vertebrate). 



