934 
ME. J. LOCKHAET CLAEKE ON THE DEVELOPJklENT OE 
ExPLANATIOIf OF THE PlATES. 
PLATE XLV. 
Fig. 1. A transverse section of the spinal column and cord in the upper part of the 
lumbar enlargement of a foetal sheep f inch in length, magnified 60 diameters ; 
— 7«, anterior white column; f, anterior grey substance ; g, anterior nerve-roots ; 
c, posterior white column ; d h', posterior grey substance ; d, posterior nerve- 
roots ; e, intervertebral ganglion ; a, epithelial layer surrounding the front of 
the canal ; j j, body of vertebra ; Jc, chorda dorsalis ; i, connective tissue 
uniting the body of the vertebra and intervertebral ganglia to the chcumference 
of the cord. 
Fig. 2. A portion of the outer surface of the posterior grey substance (b) in connexion 
with the inner surface of the posterior white column (a) ; magnified 420 dia- 
meters ; from the same foetus. 
Fig. 3. Transverse section of spinal cord in the upper part of the lumbar enlargement, 
magnified 60 diameters, from a foetal sheep 1 inch in length: — h', lateral 
column. 
Fig. 4. Transverse section of spinal cord in the upper part of the lumbar enlargement, 
magnified 60 diameters, from a foetal sheep 2 inches long: — h', lateral white 
column ; r, gelatinous substance ; p, inner portions of posterior white 
column; I b, caput cornu; n, posterior median fissure; q g, cervix cornu; 
w, w, groups of large nerve-cells of anterior cornu ; o, central canal ; m, anterior 
median fissure. 
Fig. 5. Transverse section of the spinal cord of the same foetus, from the middle of the 
dorsal region. 
Fig. 6. A similar section from the upper part of the dorsal region. 
Fig. 7. Another, from the middle of the cervical enlargement. 
Fig. 9. A portion of the section represented in fig. 8, magnified 420 diameters : — o, ante- 
rior portion of the canal ; s s, epithelium surrounding it ; f, nuclei forming 
the anterior grey substance; g, inner bundle of anterior roots entering the 
grey substance ; A, A, inner parts of the anterior white columns ; m, anterior 
median fissure between them. The epithelium is seen to be continuous on 
the one hand with the network of fibres between the nuclei of the anterior 
grey substance (f), and on the other hand with the network of pia mater (ni) 
prolonged from the circumference of the cord into the anterior median fissure. 
Fig. 9^. Fresh nerve-fibres from the sciatic nerve of a human foetus of four months : on 
the left is a single fibre ; on the right several are seen as they lie together 
constituting a nerve. 
Fig. 10. A portion of the grey substance near the edge of the posterior cornu traversed 
by fibres of the posterior roots ((7). From a foetal sheep 2-| inches long: 
magnified 670 diameters. 
