APPENDIX III 367 



DEFERO (L. to cany away), as vas deferens. 



DELPHiN (L. dolphin), in Delphinus, a cetacean. 



DELPHOS (G. uterus), a combining form; Didelphys, the opossum; Mono- 

 delphia, a variant name for Placentalia. 



DELTOID (G. fourth letter of alphabet), shaped like the letter delta, tri- 

 angular. 



DEXDRON (G. tree), a stem in dendrite, dendritic, 



DENS (L. tooth) ; dental, dentary, dentine. 



DERMA (G. skin); dermal, dermis; relating to skin. 



DERMATOME (G. derma, plus toma, a cut), the portion of the epimere 

 giving rise to the skin. 



DEVONIAN (from Devon, England, where the strata were described), a 

 Paleozoic period lying between the Silurian and Mississippian. 



Di (G. two) ; digastric, dimorphic, didelphic, diapsid. 



DiA (G. dia, between, through) ; diaphragm, diapedesis. 



DIAPHRAGM (G. dia, through, plus phragnymi, enclose), a dividing mem- 

 brane; the diaphragm of the ear; or, a muscular partition between the 

 thoracic and abdominal cavities. 



DIASTEMA (G. interval), a wide space betw^een teeth, usuallj' caused by 

 developmental suppression of the intervening teeth. 



DIGIT (L. digitus, a finger), a finger or toe; digital. 



DIMORPHISM (G. di, plus morphe, form), existing under two distinct forms. 



DiNOSAURiA (G. deinos, terrible, plus sauros, lizard), an order of extinct 

 diapsid reptiles. 



DiPLos (G. double), diploblastic, diploid. 



Dipnoi (G. di, plus pneo, to breathe), a sub-class of fishes; the lung 

 fishes with gills and lungs. 



DORSAL (L. dorsum, back), pertaining to the back of an animal. 



Duco (L. to lead), a combining form; adduct, abduct, aqueduct. 



DUODENUM (L. duodeni, from duodecim, tw'elve), the part of the intestine 

 immediately following the stomach, in reference to its length in the 

 human. 



DURA (L. hard, tough), the heavy external membrane surrounding the 

 central nervous system; dura spinalis, dura mater. 



Echidna (G. echinos, a hedgehog, or G. echidna, an adder), a genus of 



monotremes of Australasia, the spiny anteater. 

 ECT, ECTO (G. outer, outside), a prefix; ectoplasm, ectoderm. 

 ECTODERM (G. ektos, plus derma, skin), the outer cell layer of an embryo. 

 Edentata (L. e, without, plus dens, a tooth), an order of placentals with 



degenerate teeth. The order is an artificial group, and is technically 



divided into three distinct orders. 

 effector (L. ejficio, to carry out, to perform), a structure or organ 



transforming motor impulses into motor action. 

 EFFERO (L. to carry away from), a combining form; an efferent nerve or 



blood vessel leading away from a given point; efferent branchials; vasa 



efferentia. 

 ELASMO (G. elasmos, a plate), a combining form; fiat, plate-like. 

 Elasmobranchii (G. elasmos, plus branchia, gills), a sub-class of fishes 



including the sharks, skates and rays. Their skeleton is entirely of 



cartilage. Several extinct orders are known. 

 enamel (L. smaltum, enamel), the ectodermal covering of the teeth, the 



hardest substance of the body. 



