ATR- 



25 



AUT- 



room.] Pert, atrium ; appl. cavity, 

 pore, canal, siphon, lobes (zool.). 



atriocoelomic (a'trloselom'ik) a. [L. 

 atrium, central room ; Gk. koilos, 

 hollow.] Connecting the atrium 

 and the coelom ; appl. funnels, of 

 uncertain function, in Cephalo- 

 chorda (zool.). 



atriopore (a'triopor) n. [L. atrium, 

 central room ; porus, channel.] 

 The opening from the atrial cavity 

 to the exterior in Cephalochorda 

 (***), 



atrioventricular (atriove'ntrik'ular) a. 

 [L. atrium, chamber ; ventriculus, 

 small cavity.] Pert, the atrioven- 

 tricular structure in the heart ; appl. 

 bundles, groove, openings (anat.). 



atrium (a'trium) n. [L. atrium, 

 chamber.] The two anterior cavi- 

 ties of the heart ; the tympanic 

 cavity (anat.) ; a chamber surround- 

 ing the pharynx in Tunicates and 

 Cephalochordates (zoo!.). 



atrochal (at'rokal) a. [Gk. a, with- 

 out ; trochos, wheel.] Without the 

 preoral circlet of cilia ; appl. tro- 

 chophore stage when the preoral 

 circlet is absent and the surface 

 is covered uniformly with cilia 

 (zool.). 



atrophy (at'rofi) n. [Gk. a, without ; 

 trephein, to nourish.] Emaciation ; 

 diminution in size and function of 

 a part or organ (biol.). 



atropous (at'ropus) a. [Gk. a, with- 

 out ; trepein, to turn.] Appl. ovule 

 in proper position, i.e. not inverted 

 (dot.). 



atterminal (atteYmmal) a. [L. ad, 

 to ; terminus, end.] Towards a 

 terminal ; appl. current directed 

 toward the thermal cross-section 

 (Phys.\ 



attraction (atrak'shun) n. [L. at- 

 tractus, drawn to.] Any structure 

 which apparently draws other 

 things to it, as an attraction cone 

 (cyt.). 



auditory (od'itorl) a. JX. audire, to 

 hear.] Pert, the hearing apparatus, 

 appl. organ, nucleus, ossicle, capsule, 

 canal, meatus, nerve, tentacle, etc. 



Auerbach's plexus, a gangliated 

 plexus of non-medullated nerve- 

 fibres, found between the two layers 

 of the muscular coat of the small 



intestine ; the plexus myentericus 

 (Phys.). 



augmentor (ogme'n'tSr) a. [L. augere, 

 to increase.] Appl. nerves rising 

 from the sympathetic system and 

 acting on the heart, with antago- 

 nistic relation to the vagi ; ac- 

 celerator (phys.). 



aulostomatous (ol'ostom'atus) a. [Gk. 

 aulos, tube ; stoma, mouth.] Having 

 a tubular mouth or snout (zool.). 



aural (6^1) a. [L. auris, ear.] Pert. 

 ear or hearing. 



auricle (6r'lkl) n. [L. auricula, little 

 ear.] The external ear ; any ear- 

 like lobed appendage (zool.) ; the 

 upper or anterior chamber on each 

 side of the heart (anat.). 



auricula (orik'ula) n. [L. auricula, 

 little ear.] An auricle. 



auricular (ortk'ular) a. [L. auricula, 

 small ear.] Pert, an auricle ; appl. 

 artery, nerve, tubercle, vein (anat.). 



auricularia (orik'ula'ria) n. [L. auri- 

 cula, small ear.] A type of larva 

 found among the Holothurians 

 (zool.). 



auriculars, n. plu., ear coverts of 

 birds. 



auriculate (orik'ulat) a. [L. auricula^ 

 small ear.] Eared ; appl. leaf with 

 expanded bases surrounding the 

 stem ; appl. leaf with lobes separate 

 from rest of blade ; hastate-auricled 

 (dot.). 



auriculo - ventricular (6rik'ulo-vn- 

 trflc'ular) a. Pert, or connecting the 

 auricle and ventricle of the heart ; 

 appl. bundle, valve (anat.). 



aurophore (or'ofor) n. [L. auris, ear ; 

 Gk. pherein, to bear.] An organ 

 projecting from the base of pneu- 

 matophore of certain Siphonophores 

 (zool.). 



autacoid (ot'akoid) n. [Gk. autos, 

 self.] A term including both 

 hormone and chalone (phys.). 



autoblast (ot'dblast) n. [Gk. autos, 

 self; blastos, bud.] An inde- 

 pendent micro-organism. 



autocatalysis (ot'okatal'isls) n. [Gk. 

 autos, self ; kata, down ; lysis, a 

 loosing.] The dissolution or re- 

 action of a cell or substance due 

 to the influence of a product or 

 secretion of its own (phys.). 



autochthon (6tSk'th6n) n. [Gk. autos, 



