Appendix 831 



Exopodite (eks -op' o dit) (Gr, ex, out; pons, appendage), outer of two branches 



of a biramous appendage of a crustacean. 

 Exoskeleton (ek so -skel' e ton) (Gr. exo, outside), outer skeleton. 

 Expiration (ek spi -ra' shun) (Gr. ex, out; spirare, to breathe), emitting air from 



lungs. 

 Extensor (eks -ten' ser) (Gr. ex, out; tendere, to stretch), muscle to extend a limb 



or part. 

 External receptor, sense organ on surface of an organism to receive stimulation. 

 External respiration, exchange of gases between blood and the outside through 



lungs, skin, or gills. 

 Extra-embryonic coelom, one of the coeloms of the early embryo. 

 Extranuclear electrons, those outside the nucleus of the atom. 

 Eye spot, pigmented, light-sensitive area, as the stigma of Euglena. 



Fi, Fo, F3, etc., abbreviations for the first, second, third filial generations in 



heredity. 

 Factor, see Gene. 

 Facultative (fak' ul ta tiv) (L. facultas, faculty), the abiUty to change certain 



methods of living to suit conditions. 

 Fallopian tube (fa -lo' pi an) (From Fallopius, a physician who died in 1562), the 



oviduct in mammals. 

 Family (fam'ili) (L. familia, household), organisms of one group of an order. 

 Fascia (fash' i a) (L. fascia, band), bandlike covering of connective tissue. 

 Fat (A.S. faett, fat), adipose tissue, cells of which are filled with oil. 

 Fatty acid, one of a group of organic acids, such as acetic, butyric, oleic, stearic, 



etc., which contains only one COOH (carboxyl) group. 

 Fauna (fo' na) (L. Faunus, god of the woods), animal life characteristic of a 



given area. 

 Feces (fe' sez) (L. faeces, dregs), wastes or excrements. 

 Femur (fe'mer) (L. femur, thigh), thigh bone or the third segment of an insect 



leg from the proximal (near) end. 

 Fermentation (fur men -ta' shun) (L. fermentum, ferment or leaven), change in 



an organic substance caused by a ferment, as souring of milk. 

 Fertilization (fur til i -za' shun) (L. ferre, to produce), union of sperm and egg 



in sexual reproduction. 

 Fetus (foetus) (fe' tus) (L. fetus, offspring),' the later embryo of a vertebrate 



(after third month in human being). 

 Fibril (fi' bril) (L. fihrilla, small fiber), small, fibrous structure. 

 Fibrin (fi' brin) (L. fibra, band), an insoluble material in blood after clotting. 

 Fibrinogen (fi -brin' o jen) (L. fihra, thread; gignesthai, to form), a constituent 



of blood that aids in fibrin formation. 

 Fibula (fib' u la) (L. fibula, buckle), outer, smaller bone of lower leg. 

 Filial (fil' i al) (L. filia, daughter; filius, son), one or more successive generations 



after the parents. 

 Filial regression law, superior parents tend to have superior offspring but who 



on the average are less superior than the parents; inferior parents tend 



to have offspring who are also inferior, but less so than themselves. 



