636 



SPINACH 



SPINAL COLUMN 



is very generally preferred for the former purpose, 

 and the prickly Kind fur tin- latter; but a MIIIII-- 

 \vlint intermediate variety called Flanders Spinach, 

 in the seed trade named Viroffley Spinach, is now 

 often used for both, being particularly esteemed for 

 the large size of it* leaves. The native country of 

 spinach is not well known, but is believed to be 

 some part of Asia, as i lie plant was introduced by 

 the Arabs into Spain, and thence diffused over 

 Europe. Another species (.S 1 . tetrandra) is cul- 

 tivated and much esteemed in India. The name 

 spinach is also given to a number of other plants 

 of very different botanical characters, but which 

 have the same bland and nutritious qualities, and 

 are used in the same way. New Zealand Spinach 

 is Tetragonia expansa," a plant of the natural 

 order Mesembryaceie, sub-order Tetragonie;e 

 ( natural order Tetragoniaeeie of Lindley ), a trail- 

 ing, succulent annual, spreading widely over the 

 surface of the ground, and producing a great 

 abundance of stalked ovate-rhomboid leaves. The 

 young stems and leaves of this plant are much 

 used in New Zealand, and have now come into 

 very general use also in other parte of the world 

 as a kind of spinach. It is cultivated in the middle 

 and south of Europe and in Britain, succeeding 

 well even in Scotland with the slightest aid of a 

 hotbed in spring, and is found particularly useful 

 in light dry sofls, in which in summer it is diffi- 

 cult to maintain supplies of the common spinach. 

 Patience Dock, or Garden Patience ( Rumex Tnticn- 

 tia ; see DOCK ), is called in Germany English 

 Spinach, and was formerly much cultivated in 

 England, but is now neglected. 



Spinal Column and Spinal Cord. The 



spine or spinal column is the most important and 

 characteristic part of the Skeleton (q.v.) of the 

 highest division of the animal kingdom. It is com- 

 posed of a series of bones placed one above, or in 

 front of another, and called vertebrae ; and hence 

 these animals, having this distinguishing charac- 

 teristic in common, are all included in the term 

 Vertebrate*. The vertebrae vary greatly in number 

 in different animals, and even in members of the 

 same class, and the number bears no apparent 

 relation to the other organs of the animal. More- 

 over, in their shape they differ extremely even in 

 different parts of the same spine, in accordance 

 with their 8|>ecial functions. In man the number 

 of vertehne which collectively form the spinal 

 column is 7 in the neck (cervical vertebra' ), 12 in 

 the back (dorsal vertebra), 5 in the loins (lumbar 

 vertebra;), all of which are capable of being de- 

 tached from one another, and are termed true 

 vertebrae ; and 5 vertebne ossified together and 

 forming the sacrum, and 4 or 5 similarly united 

 forming the termination of the column, and consti- 

 tuting the bone called the coccyx, which are known 

 a/o/* vertebrae. However long or short the neck 

 may be, every mammal has 7 cervical vertel>r,-i-, 

 excepting the three-toed sloth which has 9, and 

 the sea-cow which has 0. In the other regions of 

 the spine no such uniformity exists. Each vertebra 

 IN attached to the two between which it lies by 

 numerous strong and more or low elastic ligaments, 

 and between each pair of vertebne there is inter- 

 posed a lenticular disc of fibro-cartilaKe, which nets 

 as a buffer. By these arrangements the spinal 

 column is rendered highly elastic, thn comninmca- 

 lion ot jars or shocks is prevented, ami a very 

 considerable general range of movement permitted, 

 although the motion between any two adjacent 

 vertelinc is slight. The elasticity of the coliimn is 

 further increased by the component vertebra; lieing 

 arranged in curves instead of being placed perpen- 

 diriilarly. The curves should be exactly in the 

 antcio posterior direction, any well-marked lateral 

 deviation from the ]>crpendicular being abnormal ; 



but a very slight lateral curvature with the con- 

 vexity to the right may often lie detected in the 

 upper and middle parts of the back, and is sup- 

 pcwed to be dependent on the more frequent use 

 and greater strength of the 

 right arm as compared 

 with the left. From their 

 po-ition they are termed 

 the cervical, dorsal, lum- 

 bar, and pelvic curves. 

 The dorsal and pelvic 

 curves have their con- 

 cavities in front, and thus 

 enlarge the spaces in which 

 the thoracic and pelvic 

 viscera are contained; the 

 two other curves are con- 

 vex anteriorly, and thus 

 afford support to the parts 

 above them. The upper 

 three curves are BO ar- 

 ranged that their cords 

 arc in the same vertical 

 line in the erect position 

 of the body, and this 

 vertical line corresponds 

 with the line of gravity 

 of the head. The cause 

 of these curves is to be 

 sought for partly in the 

 shape of the vertebral 

 lx>dics, and partly in that 

 of the intervertebral sub- 

 stance. Amongst the uses 

 of these curves it may 

 be mentioned (1) that 

 they enable the spine to 

 l>ear a greater vertical 

 weight than it could other- 

 wise maintain ; it is cal- 

 culated that nine times 

 as great a vertical force 

 is required to bend it as 

 if it had been straight ; 

 (2) that they facilitate the 

 movements of the body, 

 especially in the act of 

 running; and (3) that 

 they are so disposed as to 

 protect the cord in move- 

 ments of the spine. Simi- 

 lar curves are seen in 

 the spine of other mam- 

 mals (see ANTHROPOID 

 AI-KS), though the degree 

 of flexure is liable to great deviations. The 

 lumbar curve, which has especial reference to the 

 erect position, is always much less marked than in 

 man. 



The vertebral canal formed by the apposition of 

 the spinal foramina or neural arches, and contain- 

 ing and protecting the spinal cord, varies in it 

 size at different parts of the column. It is largest 

 in it- antero-jHwterior diameter in the neck and 

 loins (measuring at the last lumbar vertebra of 

 an inch), where the antero-posterior movements of 

 the spine are greatest, and where the cord is least 

 closely attached to the vertebrae ; while in its 

 lateral diameter it is greatest at the atlas, where it 

 measures nearly an inch and a half. A trans verse 

 section of the canal is nearly circular through the 

 ip-eater part of the back. The intervertebral fora- 

 mina through which the nerves emerge vary in 

 shape and position in different parte, but are always 

 of sufficient size to prevent injurious pressure on 

 the nerves during movement of the spine ; and in 

 tin- dorsal region, which is the ordinary scat of 

 angular curvature, the nerves are so protected by 



<C*M)\ 



Kg. 1. Spinal Column. 



