THE SPINAL COED IN MAN, MAMMALIA, AND BIEDS. 
937 
fied 420 diameters. At a the cells are in an earlier state of development, 
neither their walls nor their nuclei being yet very distinct. 
Ilg. 33. Five large and two small cells from one of the group of suboesophageal gan- 
glia of the common slug ; magnified 420 diameters. 
Fig. 34. An enormous cell from the same ; magnified 420 diameters. 
Fig. 35. Group of small cells or apparent nuclei, destined to be developed into the large 
cells of the anterior cornu, from a foetal sheep 1 inch in length. The cells 
are surrounded and connected by a delicate granular network. 
Fig. 36. Part of the spinal cord, intervertebral ganglion, and intervening pia mater 
from a foetal sheep 3 inches long ; — a a', outer surface of the cord ; b sheath 
and outer portion of intervertebral ganglion, with some of the marginal 
cells ; c d, intervening pia mater ; d, a blood-vessel cut transversely and full of 
blood-globules ; e, another blood-vessel, running round the cord : at a trans- 
verse processes are seen proceeding from the nucleated wall of the vessel to 
the surface of the cord ; at d similar processes are given off from the pia mater, 
which is merely a continuation of the nucleated walls of the vessels. On 
the other side, the pia mater and walls of the blood-vessels are seen to be 
continuous with the nucleated investment of the intervertebral ganglion, h h. 
Figs. 37 to 44 are exact representations of transverse sections of the spinal cord of a 
human foetus, all magnified about 34 diameters. The actual and relative 
quantities of the grey and white substance are well seen in each. 
Fig. 37. A transverse section of the conus medullaiis : — I 5, caput cornu posterioris j 
y, anterior comu ; o, canal ; c, posterior white column ; lateral white 
column ; h, anterior white column ; m, anterior median fissure ; posterior 
median fissure. 
Fig. 38. A transverse section through the lower third of the lumbar enlargement: — 
d, posterior nerve-roots ; q, posterior vesicular column ; w, increasing groups 
of large nerve-cells in the anterior cornu. 
Fig. 39. A similar section through the middle of lumbar enlargement. The posterior 
vesicular column {q) forming the inner half of the cervix cornu has enlarged, 
but hitherto consists chiefly of a multitude of small cells. Through it and 
on its outer side several curved bundles of the posterior roots sweep forward 
and inward, and separate it from the outer half of the cervix, at the border 
of which are several dark spots, representing the cut ends of longitudinal 
bundles. In front of the canal (o) are the decussating fibres of the anterior 
commissure, and behind it is the posterior commissure. The group of nerve- 
cells in the anterior cornu has much enlarged. 
Fig. 40. Similar section through the upper third of the lumbar enlargement. Here the 
cells of the posterior vesicular column [q) or nucleus of the cervix cornu have 
increased considerably in size : they are nearly all equal to those of the ante- 
rior cornu. The groups in the anterior cornu are much diminished. 
