VA.S- 



342 



VEL- 



vasa efferentia, the tubes which 

 lead from the testis to the vas 

 deferens (anat.). 



vasal (va'sal) a. [L. vas, vessel.] 

 Pert, or connected with a vessel. 



vascular (vas'kular) a. [L. vascuhim, 

 small vessel.] Peri., consisting of, 

 or containing vessels adapted for 

 the transmission or circulation of 

 fluid (anat ). 



vascular areas, several scattered 

 areas developed between endoderm 

 and mesoderm of yolk-sac, the 

 beginnings of primitive blood- 

 vessels (emb.). 



vascular bundle, a group of special 

 cells consisting of two parts, the 

 xylem or wood portion and the 

 phloem or bast portion ; many of 

 the vascular bundles have in addi- 

 tion a thin strip of cambium 

 separating the two parts (hot.}. 



vascular tissue, specially modified 

 plant-cells, usually consisting of 

 either tracheal or sieve cells, for 

 the circulation of sap (bot.). 



vasculum (vas'kulum) n. [L. vas- 

 culum, small vessel.] A pitcher- 

 shaped leaf or ascidium (pot.}. 



vasifactlve (vas'ifak'tiv) a. [L. vas, 

 vessel ; facere, to make.] Produc- 

 ing new blood-vessels (emb.}. 



vasiform (vas'iform) a. [L. vas, 

 vessel ; forma, shape.] Functioning 

 as or resembling a duct ; vascular 

 (biol.}. 



vasoconstrictor (vas'okonstrik'tor) a. 

 [L. vas, vessel ; constringere, to 

 draw tight.] Causing constriction 

 (Phys.}. 



vasodentine (vas'oden'tin) n. [L. 

 vas, vessel ; dens, tooth.] A variety 

 of dentine permeated by blood- 

 vessels (anat.}. 



vasodilator (vas'odila'tor) a. [L. vas, 

 vessel ; dilatus, separated.] Relax- 

 ing or enlarging the vessels (phys.}. 



vasoformative (vas'6f6r'mativ) ) see 

 vasifactive. 



vasohypertonic (vas'ohi'pe'rtonTk), 

 see vasoconstrictor. 



vasohypotonic (vas'dhl'potonlk), see 

 vasodilator. 



vasoinhibitory (vas'6'inhib'itorl), see 

 vasodilator. 



vasomotion (vas'omo'shun) n. [L. 

 vas, vessel ; movers, to move.] 



Any change in the calibre of a 

 blood-vessel (phys.}. 



vasomotor (vas'omo'tor) a. [L. vas, 

 vessel ; movere, to move.] Appl. 

 nerves supplying the muscles in 

 the wall of blood - vessels and 

 regulating the calibre of the blood- 

 vessels, through containing both 

 vasoconstrictor and vasodilator 

 fibres (phys.}. 



vastus (vas'tus) n. [L. vastus, 

 immense.] Name given to various 

 divisions or parts of the quadriceps 

 muscle of the thigh (anat.). 



vegetal pole, that side of a blastula 

 at which the megameres collect ; 

 opp. animal pole (emb.}. 



vegetation (vej'eta'shun) n. [L. 

 vegetare, to enliven.] Plants con- 

 sidered collectively. 



vegetative (vej'eta'tiv) a. [L. vegetare, 

 to enliven.] Appl. to stage of pure 

 growth in plants as opp. repro- 

 ductive ; appl. foliage shoots as 

 opp. flower or reproductive shoots 

 (hot.}. 



vegetative cone, the apical point 

 (hot.}. 



vegetative pole, see vegetal pole 

 (emb.}. 



vegetative reproduction, among 

 animals, a kind of asexual repro- 

 duction which consists in the 

 formation of buds (zool.). 



veil (val) n. [L. velum, a sail.] The 

 velum ; the calyptra (bot.) ; the 

 velum (zool.}. 



veins (vanz) n. plu. [L. vena, vein.] 

 The branched vessels which convey 

 blood to the heart (anat.} ; the 

 ribs or nervures of an insect wing 

 (zool.) ; the branching ribs or 

 nerves of a leaf (bot.). 



velamen (vela'men) n. [L. velum, 

 a sail.] A membrane (anat.) ; a 

 sheath of tracheides at the apex of 

 the aerial roots of Orchids (bot.). 



velar (ve'lar) a. [L. velum, a sail.] 

 Pert, situated near, or belonging to 

 the velum. 



velarium (vela'rium) n. [L. velum, 

 covering.] The velum of certain 

 of the Cubomedusae, which differs 

 from a true velum in containing 

 endodermic canals (zool). 



velate (ve'lat) a. [L. velum, cover- 

 ing.] Veiled ; covered by a velum. 



