MER- 



183 



MES- 



part ; zoon, animal.] A fragment 

 of a unicellular animal containing 



Eart of the macronucleus, obtained 

 y artificial division (zool.}. 



merrythought, the furcula of birds, 

 formed by the coalescence of clav- 

 icles (zool.). 



merus (me'rus) n. [Gk. meros, thigh.] 

 Meros, which see. 



mesamoeboid (meVame'boid) cells, 

 nucleated cells of the blood islands 

 from which blood corpuscles are 

 derived (emb.). 



mesarch (meVark) a. [Gk. mesos, 

 middle ; arche, beginning.] Appl. 

 xylem having metaxylem develop- 

 ing in all directions from the 

 protoxylem, characteristic of ferns ; 

 having the protoxylem surrounded 

 by metaxylem (bot.\ 



mesaxonic (meYakson'lk) a. [Gk. 

 mesos, middle ; axon, axis.] With 

 the line dividing the foot, passing 

 up the middle digit (zool.). 



mesencephalon (m6s'6nk6f'alon, -s6f-) 

 n. [Gk. mesos, middle ; en, in ; 

 kephale, head.] The mid-brain, 

 comprising corpora quadrigemina 

 (bigemina) and cerebral peduncles 

 (anat.). 



mesenchyma (me'se'ng'kima) n. [Gk. 

 mesas, middle ; engchein, to pour 

 in.] A mass of tissue, intermediate 

 between ectoderm and endoderm 

 of a gastrula (emb.). 



mesenchyme (mgse'ng'klm). Mesen- 

 chyma. 



mesenterlal (me's'e'nte'rlal, meYgnte'- 

 rlal) a. [Gk. mesos, middle ; enteron, 

 gut.] Pert, a mesentery ; appl. 

 filaments of Actinozoa (zool.). 



mesenteric (meYenteVik, mez'enteYik) 

 a. [Gk. tnesos, middle ; enteron, 

 gut.] Pert, a mesentery ; appl. 

 artery, glands, nerves, veins (anat.). 



mesenterlole (meYgnte'riol, meY- 

 Snte'rlol) n. [L. dim. of mesenterium, 

 a mesentery.] A fold of peritoneum 

 derived from the mesentery, retain- 

 ing the vermiform appendix in 

 position (anat.). 



mesenterium (me's'e'nte'rTum, meY- 

 gnte'rium) n. [L. mesenterium, a 

 mesentery.] A mesentery. 



mesenteron (me'se'n'te'rSn) n. [Gk. 

 mesos, middle ; enteron, gut.] The 

 main digestive cavity of Actinozoa 



and other Coelenterates; the portion 

 of the alimentary canal lined by 

 endoderm (zool.). 



mesentery (me's'e'nte'r!, mez'e'nte'rl) n. 

 [L. mesenterium, a mesentery.] A 

 peritoneal fold serving to hold the 

 viscera in position : there are three, 

 the mesentery proper, the trans- 

 verse mesocolon, and the sigmoid 

 mesocolon (anat.) ; a muscular par- 

 tition, complete or incomplete, ex- 

 tending inwards from the body- 

 wall in Coelenterates (zool.). 



mesepimeron (m6s'fiplm'6r6n) n. [Gk. 

 mesos, middle ; ejbi, upon ; meros t 

 part.] The epimeron of the meso- 

 thorax of an insect (zool.). 



mesethmoid (me'se'th'moid) a. [Gk. 

 mesos, middle ; etJimos, sieve ; eidos, 

 like.] Between the two ectethmoid 

 bones ; appl. ethmoid plate of 

 cranium when it ossifies (anat.) ; 

 a median cranial bone of verte- 

 brates (zool.). 



mesiad (me'zlid) adv. [Gk. mesos, 

 middle.] Towards or near the 

 middle plane. 



mesial (me'ziai) a. [Gk. mesos, middle.] 

 In the middle vertical or longi- 

 tudinal plane. 



meslan (me'zlan) a. [Gk. mesos, 

 middle.] Mesial. 



mesoarlum (mSs'oa'rlum) n. [Gk. 

 mesos, middle ; oarion, a small egg.] 

 A mesovarium. 



mesobenthos (mes'obe'n'thSs) n. [Gk. 

 mesos, middle ; benthos, depths.] 

 The animal and plant life of the 

 sea-bottom when the depth is be- 

 tween 100 fathoms and 500 fathoms 

 (zool., bot.). 



mesoblast (mes'oblast) . [Gk. mesos, 

 middle ; blastos, bud.] The meso- 

 derm or middle layer of an embryo 

 (emb.). 



mesoblastema (mes'oblaste'ma). 

 Mesoblast. 



mesoblastlc (mes'oblas'tlk) a. [Gk. 

 mesos, middle ; blastos, bud.] Pert. 

 or developing from the middle layer 

 (emb.). 



mesobranchial (mes'bbrang'klal) a. 

 [Gk. mesos, middle ; brangchia, 

 gills.] Pert, the middle gill-region, 

 as in Crustacea (zool.). 



mesobronchus (mes'obrSng'kus) . 

 [Gk. mesos, middle ; brongchos. 



