MESOSTER´NUM, _n._ Middle segment of the breast-bone.
METACAR´PAL, _a._ or _n._ Pertaining to the metacarpus; particularly the
_metacarpal_ bone.
METACAR´PUS, _n._ Hand, exclusive of the fingers; segment of the wing
between the carpus and the digits.
METAGNATH´OUS, _a._ Cross-billed; having the points of the mandibles
passing each other on the right and left.
METATAR´SAL, _a._ Pertaining to the metatarsus; particularly the
_metatarsal_ bone.
METATAR´SUS, _n._ Foot, exclusive of the toes; segment of the leg
between the tarsus and the digits, commonly called _the shank_, and in
descriptive ornithology usually known as the _tarsus_. The metatarsus,
however, has a distal tarsal ossicle confluent with it, so that it is
actually _tarso-metatarsus_. In birds, the metatarsus proper (exclusive
of the confluent tarsal bone) consists of three parallel metatarsal
bones, more or less completely confluent, and of the associated
_accessory metatarsal_ bone which bears the hallux. Compare TARSUS.
METATAR´SUS HAL´LUCIS, _n._ The accessory metatarsal bone, as just said.
MID´DLE TOE, _n._ The third toe in order of reckoning, with few
exceptions four-jointed. When the fourth toe is reversed, as in all
zygodactyle birds except trogons, it becomes the _outer_ anterior toe;
in trogons, and a few birds in which the true inner or second toe is
wanting, it becomes the _inner_ anterior toe. It is never versatile. It
rarely has only three joints, like the second toe. (128.)
MID´DLE WING-COV´ERTS, or ME´DIAN COV´ERTS. The series of upper
coverts of the secondary set, situate in one or more rows between
the greater and lesser coverts. They are usually recognized by their
overlapping each other in the reverse direction (i.e. inner border of
one overlapping outer border of the next one) from the others, whence
they are sometimes called _tectrices perversæ_. (94.)
MIGRA´TION, _n._ Periodical (but sometimes irregular) journeyings, or
change of abode, of birds at certain seasons, to secure food, climate,
or other physical conditions of environment best suited to their wants.
Migration is generally meridional (north-south), and believed by some to
be mainly accomplished along a magnetic meridian; but it is often quite
otherwise, influenced by topography, etc., or altogether capricious. In
the Northern Hemisphere, the vernal migration is northward, the autumnal
in the opposite direction.
MIME´SIS, _n._ Mimicry; mocking; simulated resemblance in voice, shape,
color, etc.
MIMET´IC, _a._ Imitative; given to mimicry. _Mimetic analogy_, simulated
resemblance in superficial respects, such as many insects bear to the
twigs or leaves they rest upon.