ME. J. L; GLAEKE OiS- THE GEEY SUBSTANCE OF THE SPINAL COED. 465 
cells ; a small group of large cells is found at its anterior extremity on each 
side. 
Fig. 24, Plate XXIV. A similar section, near the end of the conus mechdlaris of the 
Ox. It appears to be altered in shape by some accidental cause ; for in its 
natural state the canal is nearly of the same form as in fig. 23: — A, A, 
posterior white columns ; B, B, antero-lateral columns. The grey substance 
around the canal is reduced in quantity, and appears as a kind of network 
enclosing a multitude of longitudinal bundles ; it is also interspersed with 
small cells, but contains only a few of a larger kind, near its anterior 
extremity. 
Fig. 2o, Plate XXIV. Transverse section of the grey substance of t\ie Jilimi terminale, 
or filiform extremity of the cord, magnified 60 diameters. The canal is col- 
lapsed laterally, but is naturally very large, and the epithelium is consequently 
abundant. The grey substance surrounding it is reduced to a mere fringe, 
pierced here and there by small longitudinal bundles, and interspersed with 
small cells or nuclei : — a, a, processes of pia mater, and blood-vessels radiating 
from the border of the grey substance through the white columns towards 
the surface. 
Figs. 26 to 36, Plate XXIII. represent transverse sections of the spinal cord of the 
domestic Fowl. 
Fig. 26. Section at the first pair of cervical nerves. 
Fig. 27. Section in the middle of the neck. 
Fig. 28. Section at the upper end of the cervical enlargement. 
Fig. 29. Section through the middle of the ceivical enlargement. 
Figs. 30 & 31. Sections through the lower half of the cervical enlargement. 
Fig. 32. Section through the middle of the dorsal region. 
Figs. 33, 34 (& 35. Sections through the upper half of the sacral enlargement. 
Fig. 36. Section through the middle of the sacral enlargement. 
In fig. 34 the posterior median fissure (/) begins to widen towards the sur- 
face, so as to form the commencement of the sacral ventricle ; and through it 
the pia mater descends and expands into a mass which surrounds the canal, 
and replaces the posterior transverse commissure. In fig. 35 is seen an exten- 
sion of the same changes. In fig. 36 the posterior columns, with the grey 
substance, are thrown widely apart, so that the posterior median fissure 
dilates into the broadest portion of the ventricle, which is filled by a large 
mass of the pia mater (w). The lateral halves of the grey substance are con- 
sequently united only by the anterior commissure (K), in which there is a 
very evident decussation. Some of the decussating fibres may be traced into 
the cervix cornu posterioris. Metzlee, whose observations are in general in 
accordance with my own, states, however, that a real decussation is found 
only in the sacral enlargement, and in the upper part of the cervical region ; 
