MEC- 



178 



MED- 



passage.] A passage or channel, 

 as the acoustic or auditory, and the 

 nasal meatus (anat.}. 



Meckelian cartilage or rod. [After 

 Meckel, German anatomist.] The 

 lower jaw of lower vertebrates, and 

 in the higher the axis round which 

 the membrane bones of the jaw are 

 arranged and formed (anat.}. 



Meckel's rod or cartilage, Meckelian 

 rod or cartilage. 



meconidium (mgk'onid'ium) n. [Gk. 

 mekon, poppy.] Sessile or pedicel- 

 late extracapsular medusae usually 

 lying on the top of the gonangium 

 of certain Hydroids (zool.}. 



media (me'dia). [L. medius, middle.] 

 A middle structure, such as a layer 

 of tissue, a central nervure (anat., 

 zool.} ; as a plu., substances of 

 various kinds, such as bouillon, in 

 which cultures are grown (biol.}. 



mediad (me'diad) adv. [L. medius, 

 middle.] Towards but not quite in 

 the middle line or axis (anat.}. 



medial (me'dial) a. [L. medius, 

 middle.] Situated in the middle. 



median (me'dlan) a. [L. medius, 

 middle.] Lying or running in the 

 axial plane ; intermediate ; middle. 



mediastinal (me'dias'tmal, -astl'nal) 

 a. [L. mediastinus, a servant.] Pert. 

 or in the region of the mediastinum; 

 appl. cavity, arteries, glands, pleura 

 (anat.}. 



mediastinum (me'dias'tinum, -astl'- 

 num) n. [L. mediastinum, servant.] 

 The space between the right and 

 left pleura in and near the median 

 sagittal chest plane ; an incomplete 

 vertical septum of the testis (anat.}. 



mediodorsal (me'diodor'sal) a. [L. 

 medius, middle ; dorsum, the back.] 

 In the dorsal middle line. 



mediopalatine (me'dioparatin) a. [L. 

 medius, middle ; palatus, palate.] 

 Between the palatal bones ; appl. 

 a cranial bone of some Birds (zool.}. 



mediopectoral (me'diopgk'toral) a. 

 [L. medius, middle ; pectus, breast.] 

 Appl. the middle part of the sternum 

 (anat.}. 



mediostapedial (me'diostape'dial) n. 

 [L. medius, middle ; stapes, stirrup.] 

 Pert, that portion of the columella 

 auris of certain animals external to 

 the stapes (anat.}. 



mediotarsal (me'diotar'sal) a. [L. 

 medius, middle ; tarsus, ankle.] 

 Between the tarsal bones. 



medioventral (me'dioven'tral) a. [L. 

 medius, middle ; -venter, the belly.] 

 In the middle ventral line. 



medithorax (me'ditho'raks) n. [L. 

 medius, middle ; Gk. thorax, the 

 breast.] The middle part of the 

 thorax ; the mesothorax of Insects 

 (zool.}. 



medium (me'dmm) n., media (me'dia) 

 plu. [L. medius, middle.] Any of 

 the structures through which a 

 force acts, as the refracting media 

 of the eyebulb (anat.} ; any of the 

 more or less solid substances in 

 which cultures are reared or 

 tissues are propagated (phys.}. 



medulla (mgdul'a) n. [L. medulla, 

 marrow, pith.] Marrow of bones ; 

 the central part of an organ or 

 tissue (anat.} ; the pith or central 

 portion of a stem (hot.}. 



medulla oblongata, the posterior 

 portion of the brain continuous 

 with the medulla spinalis, or spinal 

 cord (anat.}. 



medullary (mgdul'ari) a. [L. medulla, 

 pith.] Pert, or in the region of 

 the medulla ; appl. axis, artery, 

 lamina, membrane, bone, spaces 

 (anat.}. 



medullary canal or cavity, the 

 hollow cylindrical portion of a long 

 bone containing marrow (anat.} ; 

 the neurocoel (emb.}. 



medullary groove, a groove on the 

 surface of the medullary plate, 

 bounded by folds which, growing 

 up, coalesce and convert the groove 

 into a canal ; the neurocoel (emb.}. 



medullary keel, a down ward growth 

 towards the archenteron, the rudi- 

 ment of the central nervous system 

 in the development of certain primi- 

 tive vertebrates (smb.}. 



medullary layer, a thick subcortical 

 layer of the thallus of some Lichens 

 (bot.}. 



medullary plate, the plate-like 

 formation of ectoderm cells 

 bordering the blastopore of early 

 embryo ; the earliest rudiment of 

 the nervous system (emb.}. 



medullary rays, a number of strands 

 of connective tissue extending be 



