Hardesty, spinal Cord of the Emu. 83 



the specimen hardened in formahn. Measurements from the 

 sections show its thickness to vary from 36 ix to 65 fi, with an 

 average thickness of 53 n. Completely fused with and contin- 

 uous with the pia mater are its three ligaments. These were 

 described by Stkeeter as occurring in the pia of the ostrich 

 cord and they are remarkably well developed in that of the 

 emu. The liganienta iongitiidiualia lateralia course along the 

 lateral surfaces of the cord proper in a line ventral to that along 

 which the dorsal and ventral nerve roots approach each other 

 (/,//, Figs. 2. 3 and 4). The hga7nentinn longitiidinale ventrale 

 {Lh, Figs. 3 and 4) is triangular or dentate in section, its apex 

 projecting into the relatively wide fissnra uicdiana ventralis. 

 Neither of these ligaments disturbs the outer contour of the 

 pia and can only be detected in the fresh by a slight difference 

 in the color of the lines it occupies. The lateral ligaments ap- 

 pear grooved into the white substance of the cord and increase in 

 thickness with tiie increase in the diameter of the cord. i. e. , from 

 the neck caudad. They appear fusiform in transverse section, 

 thinning at the edges to become continuou;; with the pia. Meas- 

 urements at their thickest part give an average thickness of 1 98 ii. 

 All three are true ligaments, being composed almost entirely of 

 large, well defined elastic tissue fibers with the characteristic 

 stellate cells in transverse section, while the pia proper is com- 

 posed mostly of white fibrous tissue. 



In addition to the usual filaments bearing blood vessels and 

 connecting the dura with the periosteum of the vertebral canal, 

 there occurs along each side of the specimen and a short distance 

 caudad to the points at which the spinal nerves penetrate the 

 dura, a series of special supporting filaments. These liganienta, 

 epiduralia occur in groups of 4 to 6 each, approximately in line„ 

 and one of them, that nearest the nerve, is always larger than, 

 the others [^Lep, Figs, i and 2) In the formalin material this, 

 larger one appears whiter than the surrounding tissue, cylindri- 

 cal and well defined, and microscopic examination reveals it to 

 be a bundle of elastic fibers. Upon opening the dura these 

 bundles along each side are found to be opposite and connected: 

 with the strongest of the ligamenta denticiilata . 



