494 PHYSIOLOGICAL SERIES. 



D. 764. Part of the spinal cord of a Turtle (Chelone my das) 

 invested in its protective membranes. Parts of the dura 

 mater have been removed, exposing the underlying pia 

 mater and the subdural space. The slenderness of the cord 

 relative to the distance between the origins of the spinal 

 nerve-roots is well shown. O. C. 1350. Hunterian. 



AVES. 



D. 765. A part of the spinal cord from the neck of an Ostrich 

 (Struthio camelus). The protecting membranes have been 

 reflected from the dorsal surface of the cord, showing the 

 longitudinal dorsal fissure extending down to the dorsal 

 grey commissure. In one part the two halves of the cord 

 have been thrust apart, rupturing this commissure and 

 exposing the central canal. Upon the ventral surface of 

 the cord the dura mater has in part been preserved. It is 

 folded back to expose the origins of the dorsal and ventral 

 roots of a pair of spinal nerves. The dorsal root is the 

 larger of the two and enters the cord by several well-defined 

 rootlets. 0. 0. 1352. Hunterian. 



D. 766. A smaller portion of the cervical region of the spinal cord 

 of an Ostrich (Struthio camelus) . The dura mater has been 

 n-movcd. In the posterior part of the specimen the right, 

 dorsal column of the cord has been cut away to show the 

 depth of the dorsal longitudinal fissure. A black bristle 

 has been inserted into the central canal. The roots of a 

 pair of spinal nerves are shown in detail. The dorsal root 

 breaks up before entering the cord into nine or ten 

 rootlets, whose several points of entrance into the cord Ho 

 in a straight line, some 15 mm. in length, upon its lateral 

 border. The ventral root rises from the cord near the mid- 

 ventral line by three main rootlets. The dorsal and ventral 

 roots run for some distance (20 mm.) before uniting. At 

 the point of union lies the large ganglion of the dorsal root. 



0. C. 1353. Hunterian. 



D. 767. A portion of the thoracic segment of the spinal cord of 

 an Ostrich (Struthio camelus) with the dura mater partly 

 removed. 0. C. 1354. Hunterian. 



