STRUCTURE OF THE BRAIN IN ROBERTS. 739 
In regions where the thalamus intervenes, as at the origin of the optic tracts, the 
lenticular nucleus retiring further outwards makes the distance between the points 
5-J- mm. In these regions the coronal fibres are distributed chiefly to the upper aspect 
of the hemisphere and not so exclusively to its marginal angle. Still further back on 
a plane with the optic radiations to the thalamus, the distance betwixt the same points 
is 6J mm., and here the great mass of the projection system no longer runs upwards 
to the vertex, but immediately upon the emergence from the lenticular nucleus they 
bend directly backwards towards the occiput and are therefore exhibited as transverse 
sections of fasciculi (Plate 49, fig. 10, F). A limited supply can still be traced 
upwards to the cortex of the outer and upper aspect of the hemisphere (Plate 49, 
fig. 10, A). These facts warrant us in asserting— 
1st. In regions anterior to the thalamus the coronal connexions betwixt cortex and 
motor ganglia with the internal capsule, arise par excellence from that marginal aspect 
of the vertex whose cortex is characterised by the great ganglionic cell formation, and 
as entering into the composition of Ferrier’s motor realm. 
2nd. That the median cortex (upper limbic arc) has no connexion with the same 
ganglia or capsule throughout any of its course. 
3rd. That as these ganglia retire outwards before the intervening thalamus, their 
coronal connexions arise chiefly from the upper and outer aspect of the hemisphere 
and still further back from the occipital cortex at their own level. 
From what has already been stated as regards the distribution of the callosal 
commissure, it is evident that in the anterior regions of the brain the marginal and 
exposed aspect adjacent to it will receive a much larger supply of medullated fibres 
than with the more external aspect, or the cortex of the median aspect, which receives 
callosal fibres only. In accordance with this a glance at vertical sections of fresh 
brain shows the dense sheaves of fasciculi which radiate to the marginal angle 
(Plate 49, fig. 11, E), and the comparative paucity of medullated supply to the limbic 
arc and outer aspect of hemisphere. 
Junction of 'projection fasciculi icith motor ganglia .—The uniform medullary 
radiations unite into delicate fasciculi which pass between the fibres of the callosal 
commissure, decussating with them at various angles, and just where they arrive at 
the surface of the striate ganglion unite into coarser fasciculi and pass into the outer 
segment of the ganglion, often bending in wands at right angles to their original 
course (Plate 49, fig. 11, C). The fasciculi thus formed by convergence of the coronal 
radiations have an average diameter of *05 mm., but towards the upper pole of the 
lenticular nucleus large fasciculi are found with a diameter of '093 mm., much more 
closely aggregated. At the lowest level of this body they form long delicate bundles 
('025 mm. diameter), which pass uninterruptedly after a straight or curved course into 
its inner segment, whilst midway betwixt these points the fasciculi are far more 
widely scattered apart and are of medium size (Plate 49, fig. 13, A-B). The 
delicate bundles traversing tbe callosal fibres which by their convergence form the 
