OF THE BACK. 357 



surface of the lamina of the vertebra above, the fibres extending as far inwards 

 as the root of the spinous process. The first is found between the first and 

 second dorsal; the last, between the eleventh and twelfth. Sometimes the 

 number of these muscles is diminished by the absence of one or more from the 

 upper or lower end. 



The Supraspinales consist of a series of fleshy bands, which lie on the spinous 

 processes in the cervical region of the spine. 



The Interspinales are short muscular fasciculi, placed in pairs between the 

 spinous processes of the contiguous vertebrae. In the cervical region theyare 

 most distinct, and consist of six pairs, the first being situated between the axis 

 and third vertebra, and the last between the last cervical and the first dorsal. 

 They are small, narrow bundles, attached, above and below, to the apices of the 

 spinous processes. In the dorsal region they are found between the first and 

 second vertebrae, and occasionally between the second and third; and below, 

 between the eleventh and twelfth. In the lumbar region there are four pairs of 

 these muscles in the intervals between the five lumbar vertebrae. There is also 

 occasionally one in the interspinous space, between the last dorsal and first 

 lumbar, and between the fifth lumbar and the sacrum. 



The Extensor Coccygis is a slender muscular fasciculus, occasionally present, 

 which extends over the lower part of the posterior surface of the sacrum and 

 coccyx. It arises by tendinous fibres from the last bone of the sacrum, or first 

 piece of the coccyx, and passes downwards to be inserted into the lower part 

 of the coccyx. It is a rudiment of the extensor muscle of the caudal vertebras 

 which exists in some animals. 



The Intertransversales are small muscles placed between the transverse pro- 

 cesses of the vertebra. In the cervical region they are most developed, con- 

 sisting of two rounded muscular and tendinous fasciculi, which pass between 

 the anterior and posterior tubercles of the transverse processes of two contiguous 

 vertebras, separated from one another by the anterior branch of a cervical nerve, 

 which lies in the groove between them, and by the vertebral artery and vein. 

 In this region there are seven pairs of these muscles, the first being between 

 the atlas and axis, and the last between the seventh cervical and first dorsal 

 vertebrae. In the dorsal region they are least developed, consisting chiefly of 

 rounded tendinous cords in the intertransverse spaces of the upper dorsal ver- 

 tebrae; but between the transverse processes of the lower three dorsal vertebrae 

 and the first lumbar they are muscular in structure. In the lumbar region they 

 are four in number, and consist of a single muscular layer, which occupies the 

 entire interspace between the transverse processes of the lower lumbar vertebrae, 

 whilst those between the transverse processes of the upper lumbar are not 

 attached to more than half the breadth of the process. 



The Rectus Capitis Posticus Major arises by a pointed tendinous origin from 

 the spinous process of the axis, and, becoming broader as it ascends, is inserted 

 into the inferior curved line of the occipital bone and the surface of bone im- 

 mediately below it. As the muscles of the two sides ascend upwards and out- 

 wards, they leave between them a triangular space, in which are seen the Eecti 

 Capitis Postici Minores muscles. 



Relations. By its superficial surface, with the Complexus, and, at its insertion, 

 with the superior oblique. By its deep surface, with the posterior arch of the 

 atlas, the posterior occipito-atloid ligament, and part of the occipital bone. 



The Rectus Capitis Posticus Minor, the smallest of the four muscles in this 

 region, is of a triangular shape; it arises by a narrow pointed tendon from the 

 tubercle on the posterior arch of the atlas, and, becoming broader as it ascends, 

 is inserted into the rough surface beneath the inferior curved line, nearly as far 

 as the foramen magnum, nearer to the middle line than the preceding. 



Relations. By its superficial surface, with the Complexus. By its deep sur- 

 face, with the posterior occipito-atloid ligament. 



The Obliquus Inferior, the larger of the two oblique muscles, arises from the 



