MID- 



193 



MIX- 



mid-rib, the large central vein of a 

 leaf, the continuation of the petiole 

 (bot.}. 



midriff (mid'rif) n. [A. S. mid, middle ; 

 hrif, the belly.] The diaphragm or 

 muscular partition between the 

 thoracic and abdominal cavities 

 (anat., zool.}. 



Miescher's tubes, see Ralney's 

 tubes. 



migration (migra'shun) n. [L. 

 migrare, to transfer.] Change of 

 habitat, according to climate or 

 food-supply, observable chiefly in 

 birds, also in reindeer, bats, certain 

 fishes, etc. (zool.}. 



migratory cell, an amoeboid cell or 

 leucocyte of the blood. 



miliary (mil'iar!) a. [L. milium, 

 millet.] Of granular appearance ; 

 small and numerous (zool.}. 



milk-teeth, the first dentition of 

 Mammals, shed soon after or before 

 birth. 



milt (milt) . [A.S. tnilte, the spleen.] 

 The spleen. 



milt (milt) n. [A corruption of milk, 

 due to confusion with milt, the 

 spleen.] The soft roe, or male 

 generative organ of Fishes. 



mimetic (mfmgt'ik) a. [Gk. mimet- 

 ikos, imitative.] Appl. animals 

 and plants which practise mimicry 

 (biol.}. 



mimic (mim'lk) v. [Gk. mimikos, 

 imitating.] To assume, usually for 

 protection, the habits, colour, or 

 structure of another organism 

 (zool.}. 



mimicry (mim'ikri) n. [Gk. mimikos, 

 imitative.] Assumption of resem- 

 blance in colour or structure as a 

 means of self-protection (dial.}. 



mine (mm) n. [L. minare, to con- 

 duct.] A tunnel or gallery con- 

 structed by an insect (zool.}. 



minimus (min'imus) n. [L. minimus, 

 least.] The fifth digit of hand or 

 foot. 



Miocene (ml'osen) a. [Gk. melon, 

 less ; kainos, recent.] Appl. the 

 eleventh of the thirteen rock- 

 systems, and belonging to the 

 Cainozoic or Tertiary group (pal.}. 



miostemonous, meiostemonous 

 (Art). 



miracidium (mTr'asTd'ium) n. [Gk. 



dim. of meirakion, a stripling.] 

 The ciliated embryo or youngest 

 stage in the life-history of a Trema- 

 tode (zool.}. 



mitochondria (mi'tokon'dria) n. plu. 

 [Gk. mitos, thread ; chondros, grain.] 

 Ergastoplasmic granulations of 

 protozoan protoplasm ; sphero- 

 plasts (zool.} ; a rounded mass of 

 granules or fibrils near the nucleus 

 of pancreas cells (anat.}. 



mitochondrial sheath, an envelope 

 containing mitochondrial granules 

 sheathing the spiral thread of a 

 spermatozoan body or connecting 

 piece (emb.}. 



mitome (ml'tom) n. [Gk. mitos, 

 thread.] The reticulum of cell- 

 protoplasm, as opposed to ground- 

 substance (biol.}. 



mltoschisis (mitos'krsls) n. [Gk. 

 mitos, thread ; schizein, to cleave.] 

 Indirect nuclear division ; mitosis 



mitosis (mito'sts) n. [Gk. mitos, 

 thread.] Indirect or karyokinetic 

 nuclear division, with chromosome- 

 formation, spindle-formation, and 

 with or without centrosome activity, 

 and final reduction of the chromo- 

 somes (cyt.}. 



mitosome (mit'osom) n. [Gk. mitos, 

 thread ; soma, body.] A body 

 arising from the spindle-fibres of 

 secondary spermatocytes, eventu- 

 ally said to form the connecting 

 piece and tail envelope of the 

 spermatozoon (zool.}. 



mitotic (mitot'ik) a. [Gk. mitos, 

 thread.] Pert, or produced by 

 mitosis ; appl. division, figure, 

 phase (biol.}. 



mitra (mi'tra) n. [L. mitra, head- 

 band.] A helmet-shaped part of 

 calyx or corolla ; the mitriform 

 pileus of certain Fungi (bot.}. 



mitral cells, pyramidal cells with 

 thick basal dendrites, found in the 

 molecular layer of the olfactory 

 bulb (anat.}. 



mitral valve, the bicuspid valve, 

 guarding the left auriculo-ven- 

 tricular orifice of the heart (anat.}. 



mitriform (mit'riform) a. [L. mitra, 

 head-band ; forma, shape.] Mitre- 

 shaped. 



mixipterysrium (mlk'sIpteYIj'Ium) //. 

 N 



