spinage

See spinach. spinal (spinal), a. [= F. spinal = Sp. espinal = Pg.espinhal = It. spinale, IMG:content-1750.png:[blocks in formation] C C 1 cd 8 Human Spinal Column. cd 8 Spinax sacral. Twenty-four of its bones are individually movable. The total length averages 26 or 27 inches. See ver tebra, and cut under backbone. - Spinal cord, the main neural axis of every vertebrate, exclusive of the brain; the myelon, or the neuron without the encephalon; the spinal marrow, or nervous cord which extends in the spinal canal from the brain for a varying distance in different animals, and gives off the series of spinal nerves in pairs. The cord is directly continuous with the brain in IMG:content-1751.png:[blocks in formation] the brain, constitutes the neuron, or cerebrospinal axis, developed from an involution of epiblast in CPT connection with a notochord (see cut under protoverte bra ). The cord is primitively tubular, and may re tain, in the adult, traces of its cœlia (see rhombocœlia ), comparable the cœliæ of the brain; but it generally solidifies, and also parallel columns, between certain of which IMG:content-1752.png:[merged small][ocr errors][merged small][merged small] AT IMG:content-1753.png:[ocr errors][merged small][merged small][merged small][merged small][merged small][merged small] Cro -section of Human Spinal Cord. AC, anterior column; AF, anterior fi ure; AGC, anterior gray commi ure; AH, anterior horn of gray matter; AR, anterior roots; AT, ascending anterolateral tractor tract of column, or becomes fluted, or umn of Burdach; Can., central canal; CC, presents several Clarke's column; CPT, cro ed pyramidal tract; CT, cerebellar tract; DPT, direct or uncro ed pyramidal tract; DT, anterolateral descending tract; GC, posteromedian column, or column of Goll; L, Li auer's tract; LC, lateral column; LH, lateral horn or intermediolateral tract of gray matter with contained ganglion-cells; PC, posterior column; PF, posterior fi ure; PGC, posterior gray commi ure; PR, posterior root; SG, subs tanti a gelati nos a; WC, anterior white commi ure. the spinal nerves emerge. In man the cord is solid and subcylindri cal, and extends in the spinal ca nal from the foramen magnum, where it is continuous with the oblong at a, to the first or second lumbar vertebra. It gives off the spinal nerves, and may be regarded as made up of a series of segments, from each of which springs a pair of nerves; it is divided into cervical, thoracic, lumbar, sacral, and coccygeal regions, corresponding to the nerves not to adjacent vertebræ. is an enlargement where the nerves from the arms come in (the cervical enlargement), and one where those from the legs come in (the lumbar enlargement). A cro -section of the cord exhibits a central H-shaped column of gray substance incased in white. (See figure.) tracts functions are exhibited on one side of the cut; they are not distinguished in the adult healthy cord, but differ from one another in certain periods of early development, and may be marked out by secondary degenerations. The cord is a center for certain reflex actions, and a collection of pathways to and from the brain. The reflex centers have been located as follows: scapular, 5 C. to 1 Th.; epigastric, 4 Th. to 7 Th.; abdominal, 8 Th. to 1 L.; crem a steric, 1 L. to 3 L.; patellar, 2 L. to 4 L.; cystic and sexual, 2 L. to 4 L.; rectal, 4 L. to 2 S.; gluteal, 4 L. to 5 L.; Achilles tendon, 5 L. to 1 S.; plantar, 1 S. to 3 S. See also cuts under brain, cell, Petromyzontidæ, and Pharyngobranchii. - Spinal epilepsy, muscle-clonus, spontaneous or due to a uming some ordinary position of the legs, the result of increased myotatic irritability, as in spastic paralysis.Spinal foramina, the intervertebral foramina. - Spinal ganglia. See ganglion.-Spinal marrow. Same as spinal cord. - Spinal muscles, the muscles proper of the spinal column, which lie longitudinally along the vertebræ, especially the epaxial muscles of the back, constituting what are known in human anatomy as the third, fourth, and fifth layers of muscles of the back (the so-called first and second "layers" of human anatomy being not axial, but appendicular). One of these is called spinal is. Spinal nerves, the numerous pairs of nerves which arise from the spinal cord and emerge from the intervertebral foramina. In the higher vertebrates spinal nerves originate by two roots from opposite sides of that section of the spinal cord to which they respectively pertain a posterior, sensory, or ganglionated root, and an an terior, motor, or non - ganglionated root, which usually unite in one sensorimotor trunk before emergence from the intervertebral foramina, and then as a rule divide into two main, trunks, one epaxial and the other hypaxial. The number of spinal nerves varies within wide limits, and bears no fixed relation to the length of the spinal cord, which latter may end high in the dorsal region, yet give off a leash of nerves (see cauda equina, under cauda ) which emerge from succe ive intervertebral foramina as far as the coccygeal region. The spinal nerves form numerous and intricate connections with the nerves of the ganglionic system. Their epaxial trunks are always few and small in comparison with the size, number, and extent of the ramifications of the hypaxial trunks, which latter usually supply all the appendicular and most of the axial parts of the body. - Spinal reflexes. See reflex. - SpiInal veins, the numerous veins and venous plexuses in and on the spinal column, carrying off blood from the bones and included structures. In man these veins are grouped and named in four sets. See vena. A, side view; B, same, in median sagittal section; C, front view; c, seven cervicals; d, twelve dorsals; 7, five lumbars; s, five sacrals, fused in a sacrum; cd, four caudals or coccygeals, forming a coccyx. flexible column capable of bending, as a whole, in every direction. It is most movable in the lumbar and cervical regions, le so in the dorsal and coccygeal, fixed in the spinal is (spi-nāʻlis), n.; pl. spinales (-lēz). [NL. (sc. musculus ),