mesopterygium 
NL. pterygium.] The middle one of several 
basal cartilages which the pterygium of a fish, 
as an elasmobranch, may present, between the 
propterygium and the metapterygium. See 
pterygium. 
mesopterygoid (mes-op-ter'i-goid), n. [NL., < 
Gr. ficaog, middle, + NL. pterygoid, q. v.] That 
part of the pterygoid which in birds articulates 
with the palatal bone or with the basipterygoid 
process of the sphenoid, or with both. 
mesopycni (mes-o-pik'ni), n. pi. [ML., < Gr. 
piaoc, middle, + TTVKV&V, a small interval in mu- 
sic, neut. of irvKv6; t close.] In medieval music, 
modes based upon a tetrachord having its half- 
step in the middle. 
mesorchial (rnes-or'ki-al), a. [< mesorchium + 
-a/.] Of or pertaining to the mesorchium. 
mesorchium (mes-6r'ki-um), n. ; pi. mesor- 
chia (-a). [NL., < Gr. fieaof, middle, + opxv, a 
testicle.] In anat., the fold of peritoneum sup- 
porting the testis while in the abdomen, or as 
it descends into the scrotal sac. 
mesorectal (mes-o-rek'tal), . [< mesorectum 
+ -al.] Of or pertaining to the mesorectum. 
mesorectum (mes-o-rek'tum), .; pi. mesorec- 
to (-tg 1 )- [NL., < Grr. peaof, middle, + NL. rec- 
tum, q. v.] The mesentery of the rectum; the 
fold of peritoneum which is reflected over part 
of the rectum, holding this gut in place. 
mesoretina (mes-o-ret'i-na), n. [NL., < Gr. 
,fo-of, middle, + NL. retina, q. v.] The middle 
stratum, or mosaic layer, of the retina, com- 
posed of the rod and cone and nuclear layers. 
J. Leidy, Anat., 1889. 
mesortiinal (mes-o-ri'nal), . [< mesorliine 
+ -al.] Internasal; internarial; situated be- 
tween the nostrils : said specifically of the meso- 
rhinium. 
mesorhine (mes'o-rin), . [Properly mesorrhine 
(cf . Gr. [u:a6ppiv, having a middling nose), < Gr. 
//woe, middle, + pif (piv-), nose.] Having an in- 
dex ranging from 48 to 53 : applied to the nose, 
or to a person having such a nose. 
Nose small, niettorhina or leptorhine. W. H. Flower. 
mesorhinian (uies-o-riu'i-an), a. [< mesorliine 
+ -tan.] Same as mesorhme. Nature, XXXV. 
357. 
mesorhinium (mes-o-riu'i-um), n. ; pi. meso- 
rkinia (-a). [NL., < Gr. iieao^, middle, + pif 
(piv-), the nose.] In ornith., the part of a bird's 
beak which is situated between the external 
nostrils ; the basal or iuternarial part of the 
culmen. In some birds it runs up on the forehead, mag- 
nified or otherwise diversified, giving riae to the frontal 
shield or casque. See cute at antice and shield. 
mesoscapula (mes-o-skap'u-la), n.; pi. meso- 
scapulie (-le). [NL.', < Gr. licaof, middle, + NL. 
scapula, q. v.] The spine of the scapula, con- 
sidered as a median element of that bone. W. 
K. Parker. Delta mesoscapulse. See delta. 
mesoscapular (mes-o-skap'u-lar), a. [< meso- 
scapula + -nr 3 .] Of or relating to the meso- 
scapula. 
At the scapular extremity of the clavicle there is often 
a piece of cartilage, considered to .be segmented off from 
the end of the mesoscapula, and hence called meioicamdar 
segment W. H. Flower. 
mesoscuta, . Plural of menoscutum. 
mesoscutal (mes-o-sku'tal), a. [< mesoseutum + 
-al.] Of or pertaining to the mesoscutum. 
mesoscutellar (mes-o-sku'te-lar), a. Of or per- 
taining to the mesoscutellum.' 
mesoscutellum (mes"o-sku-terum), .; pi. mes- 
oscutella (-a). [NL., <' Gi.'^ao^, middle, + NL. 
scutellum, q. v.] In eh torn., the scutellum of the 
mesonotum ; the scutellar sclerite of the meso- 
thorax. 
mesoscutum (mes-o-sku'tum), n.; pi. mesoscuta 
(-tii). [NL., < Gr. |Uto-oc, middle, + NL. scutum, 
q.v.] Jnentom., the scutum of the mesonotum ; 
the scutal sclerite of the mesothorax. 
mesoseme (mes'o-sem), a. [< Gr. jUfuof, mid- 
dle, + ajj/ia, a sign, mark, token.] In cmniom., 
having an orbital index between 84 and 89. 
Mesosemia (mes-o-se'mi-a), n. [NL., < Gr. 
/teo-of, middle, -t- af/pa, a sign, mark, token.] A 
genus of South American butterflies of the fami- 
ly Erucinidtv. It contains many brown or blue species, 
striped with black, and usually having a large round black 
spot in_the middle of the fore wing. 
mesosiderite (mes-o-sid'e-rlt), . [< Gr. fie<roc, 
middle, + aiomtnK, of iron: see siderite.] A 
name given by G. Rose (1864) to one of three sub- 
divisions made by him in the classification of 
meteoric irons, these divisions being founded 
on the comparative amount of iron and stony 
matter present. As defined by Brezina, in one of the 
most recent systematic classifications of the meteorites, 
3726 
te is a network of iron inclosing olivin and bronz- 
ite with more or less plagioclase, these minerals having so 
coarsely crystalline a texture that the characteristic struc- 
ture is obscured. It forms a passage from the iron to the 
chondrites. The meteorite which fell at Estherville, Iowa, 
in 1879 is of this class. See meteorite. 
mesosigmoid (mes-o-sig'moid), n. [< Gr. [ttaof, 
middle, + E. sit/moid.] The mesentery of the 
sigmoid flexure of the intestine, between the 
mesocolon and the mesorectum. 
mesosoma (mes-o-so'ma), n. ; pi. mesosomata 
(-ma-ta). [NL., < Gr. /ilaof, middle, + aa/ia, 
the body.] In lamellibranchiate mollusks, a 
middle region of the body, which gives rise to 
the foot and is situated Between the prosoma 
and the metasoma. 
mesosomatic (mes"o-so-mat'ik), a. [< meso- 
soma(t-) + -ic.] Of or pertaining to the meso- 
soma of a mollusk. 
mesosperm (mes'o-sperm), . [< Gr. ftiaof, 
middle, + tmep/ui, seed.] In bot., a membrane 
of a seed; the secundine, or second membrane 
from the surface. 
mesospore (mes'o-spor), . [NL.. < Gr. /itaof, 
middle, + OTTO/JOC, seed.] The middle coat or 
laj^er of a spore when it is possible to distin- 
guish three layers, as in the spores of Onoclea 
Struthiopteris. 
mesosporic (mes-o-spo'rik), a. [< mesospore + 
-ic.] Of or pertaining to the mesospore. 
mesostaphyline (mes-o-staf'i-lin), a. [< Gr. 
litaof, middle, + ara^v'/.ii, the uvula.] In cra- 
niom., intermediate between leptpstaphyline 
and brachystaphyline that is, with a palate 
of median width; having a palatal index of 
from 80 to 85. 
mesostate (mes'o-stat), . [< Gr. /-<rof , middle, 
+ E. state.] In biol., an intermediate sub- 
stance or product in a series of metabolic 
changes. 
We are thus led to the conception that the specific ma- 
terial of a secretion, such as the trypsin of pancreatic 
juice, comes from the protoplasm of the cell, through a 
number of intermediate substances, or mesnstates as they 
are called. M. Fatter, Encyc. Brit., XIX. 19. 
mesosterna, n. Plural of mesosternum. 
mesosternal (mes-o-ster'nal), a. [< mesoster- 
num + -al.] Of or pertaining to the mesoster- 
num : as, a mesosternal sternite. 
mesosterneber (mes-o-ster'ne-ber), . [< 
NL. mesostcrnebra, < Gr. /icaof, middle, + NL. 
xternebra, sterneber : see sterneber.] Any one of 
the intermediate sternebers or pieces of the 
breast-bone which intervene between the rnanu- 
brium of the sternum and the xiphoid or ensi- 
form appendage. There are usually several 
such bones in mammals and various reptiles, as 
the four composing the gladiolus in man. 
mesosternebra (mes-o-ster'ne-brii), n.; pi. mes- 
osternebra! (-bre). [NL.] Same as mesoster- 
neber. 
mesosternebral (mes-o-ster'ne-bral), a. [< 
mesosterneber + -al] 'Pertaining to a meso- 
sterneber. 
mesosternum (mes-o-ster'num), .; pi. meso- 
xterna (-na). [NL., '< Gr. fieaof, middle, + NL. 
sternum, q. v.] I. In anat., the 
piece or pieces of a breast-bone 
which has several segments lying 
between the presternum and the 
xiphisteruum : said chiefly of the 
segmented sternum of mammals. 
In man it is the gladiolus or body of the 
sternum proper, as distinguished from the 
manubrium and the xiphoid cartilage. 
2. In entom., the ventral or sternal 
sclerite of the mesothorax ; the un- 
der side of the mesothorax, opposite 
the mesonotum. 
mesostethium (mes-o-ste'thi-um), 
. ; pi. mesostethia (-a). [NL., < 
Gr. ("taof, middle, + aryOiov, dim. of 
aTrfiof, the breast.] In entom., the 
metasternum, or large piece be- 
tween the bases of the middle and 
the posterior legs. It is conspicu- 
ous in beetles. Kirby. 
mesostylous (mes-o-sti'lus), a. [< 
Gr. fieoos, middle, +' OTV/.OC, a pillar: 
see style?.] Same as mitl-sti/led. Kdage 
See lieterustiilism. 
Mesosuchia (mes-o-su'ki-a), . pi. [NL., < Gr. 
/teaof, middle, + mvxof, a crocodile (a local 
name in Egypt).] Adi vision of crocodiles having 
amphicoelous vertebra; : contrasted with EHKH- 
cJiia and Parasitchia. 
mesosuchian (mes-o-su'ki-au), u. [< 
chia + -an.] Of or pertaining to tlie 
chin. 
Sternum uf 
PiU, showing 
tt, niesoster 
i unn or gladio 
lus; ps, pre 
sternum or in 
nubrium ; j 
xiphisternu 
mesotympanic 
Orocodilians have developed into the Mewsiichian type. 
(Jiinther, Encyc. Brit., XX. 166. 
mesosuchious (mes-o-su'ki-us), . [< Meanxu- 
rliiii + -ous.] Same as mesosuchian. 
mesotarsus (mes-o-tar'sus), .; pi. mesotarsi 
(-si). [NL., < Gr./ifo-of, middle, + NL. tarsus, 
q. v.] In ftitom., the whole tarsus of the second 
or middle leg of a six-footed insect, coming be- 
tween the metatarsus of the hind leg and the 
protarsus of the fore leg. 
mesothelial (mes-o-the'li-al), a. [< mesothr- 
lium + -at.] Of or pertaining to mesothe- 
lium. 
mesothelium (mes-6-the'li-um), . [NL., < Gr. 
fteaof, middle, + NL. (epi)tlieliitm, q. v.] The 
epithelium lining the entire primitive coelom 
or body-cavity of the embryo; the coelarinm. 
Mesotheriidae (mes"o-the-ri'i-de), n.pl. [NL.,< 
Mesotlierium + -ida:] A family of extinct quad- 
rupeds from the Pliocene of South America, 
representing a very generalized type, allied on 
the one hand to the rodents and by some made 
a suborder, Hebetidentati, of Sodetttia, by oth- 
ers referred to the SttbtHtguiata or polydactyl 
ungulates. There are clavicles, as in no other known 
ungulates, and four lower incisors, as in no known ro- 
dents ; the nrandibular condyle is transverse, and the max- 
illaries articulate with the nasals. There are in each up- 
per half-jaw 1 incisor, no canines, 2 premolars, and a mo- 
lars, and in each lower half-jaw 2 Incisors, no canines, 1 
premolar, and 3 molars in all, 24 teeth, 
Mesotherium (mes-o-the'ri-um), H. [NL., < 
Gr. /ieo-of , middle, + dqpiov, a wild beast.] A ge- 
nus of fossil rodent-like ungulate quadrupeds, 
typical of the family Mesotheriida?, upon which 
is based the prime division Bebetidentati. M. 
cristatum is the type species. Typotheriinn is 
a synonym. 
mesotherm (mes'o-therm),)(. [= F.M&pfterme, 
< Gr. /jeaof, middle, + feftuof, hot, 6tp/n}, heat.] 
In Alphpnse de Candolle's classification of 
plants with regard to their geographical distri- 
bution, a plant of his third "physiological 
group." The plants of this group require a moderate 
degree of heat, from 15 to 20' C. They are very numerous, 
including most of the plants of the warmer parts of the 
temperate zones of both hemispheres exclusive of the 
mountainous districts. 
mesothesis (me-soth'e-sis), . [< Gr. utarx;, 
middle, + Benic, a putting, proposition : see 
thesis.'] Middle place ; mean. [Bare.] 
Imitation is the metathesis of likeness and difference. 
Coleridgf. 
mesothoracic (mes"o-th6-ras'ik), . [< mesa- 
thorax (-ac-) + -ic.] Of or pertaining to the 
mesothorax of an insect Mesothoracic case. 
Same as mesothoracotheca. 
mesothoracotheca (mes-o-th6"ra-ko-the'ka). 
n. ; pi. mesothoracothecce (-se). [NL., < meso- 
thorax (-ac-) + Gr. 6f/Kri, a case.] In entom., the 
mesothoracic case, or that part of the integu- 
ment of a pupa covering the mesothorax. In the 
Lepidoptera and Diptera the other thoracic cases are in- 
distinguishable from this, and it is then called the thn- 
racotheca. 
mesothorax (mes-o-tho'raks), . [NL.,<Gr.//f- 
aof, middle, + Bupat-, chest: see thorax.] In en- 
torn., the second or 
middle one of the 
three divisions of the 
thorax, situated be- 
tween the prothorax 
and the metathorax, 
and bearing the sec- 
ond pair of legs and 
the first pair of wings. 
When very large, as in 
dipterous insects, it is 
simply called the tho- 
rax. 
mesotrocha (me-sof- 
ro-ka), . pi. [NL., 
< Gr. fieaof, middle, + 
Tpo^of , anything roun d 
or circular: see tro- 
chee.] Ciliated embryos of polychsetpus anne- 
lids in which one or many bands of cilia encir- 
cle the middle of the body. See atroclm, telr- 
otrocha. 
mesotrochal (me-sot'ro-kal), a. [< mesotrochti 
+ -al.] Pertaining to or resembling mesotro- 
cha ; mesotrochous. 
The actively locomotive embryo of Sipunculus . . . re- 
sembles a Rotifer or a mesotrochal annelidan larva. 
Huxley. Anat, Invert., p. 217. 
mesotrochous (me-sot'ro-kus), a. [As - 
sotrocna + -ous.] Same as mcsotroclial . 
mesotympanic (mes"o-tim-pan'ik), a. and n. 
[< Gr. picof, middle, + Ti'ii-mw, a drum (see 
tympanum), + -ic.] I. n. Situated in the 
Mesothorax, shaded, between 
prothorax (a) and metathorax 
(*) ; f, head; if, two abdominal 
segments. 
