Hardest Y, Spinal Cord of the Enm. 91 



Such swellings, though discernable, were not so marked in this 

 region of the emu cord as his illustration shows them for the 

 ostrich. However, in the longer segments of the emu cord 

 there are indications of segmental arrangement not described by 

 Streeter for the ostrich. These appear in the specimen as 

 slight enlargements either at or. in the upper segments, just 

 caudad to the levels at which the nerve roots pass through the 

 dura mater. They are sufficiently evident to be easily noted in 

 the fresh specimen both with the dura intact and after it has 

 been removed. They are formed by a somewhat gradual in- 

 crease in the diameter rather than as bulbous swellings and 

 they are evident from the dorsal aspect as well as from the ven- 

 tral and lateral views of the specimen ( Se, Fig. i ). 



The appearance is more marked before the dura is remov- 

 ed. This is due to the dorsal and ventral root fibers collecting 

 beneath the dura to form the roots, as may be seen in Figure 2, 

 which is a lateral longitudinal section passing- along the line of 

 formation of the ventral roots. It is most apparent in the longest 

 segments where the nerves are considerably apart, while obvi- 

 ously in the shorter segments it becomes less discernable or not 

 at all, owing to the fusion of adjacent swellings. 



By comparison of transverse sections through the different 

 levels of a segment the nature of the segmental enlargements 

 maybe observed and their extent determined. Figure 3, Se, 

 represents a stained transverse section taken just below the lev- 

 el at which the 22nd pair of nerves is attached, or the level cor- 

 responding to that indicated by Se, figure 2, which is a longi- 

 tudinal section of the 20th segment. Figure 3, M, is a trans- 

 verse section of the 22nd segment midway between the nerves 

 (level M, fig. 2). Figure 4, Se and M, represent similar sections 

 from the 17th segment. It is seen at once that the Se sections 

 are of appreciably greater diameter than those designated by 

 J/ and that the increase involves both diameters of the speci- 

 men. The following measurements of a {^w of the segments 

 indicate the extent of the segmental enlargements. They are 

 made from stained and mounted transverse sections and are ex- 

 clusive of the dura mater. 



