760 
MR. A. SANDERS ON THE ANATOMY OF THE 
in the Carp. They are the bodies termed by Haller “ cornu ammonis,” and I have 
reason to suppose that they form the peculiar organ found in the brain of the Mor- 
myridce, as I have before mentioned. 
Tuberosities of the Vagus and the Medulla Oblongata. 
The tuberosities of the vagus (fig. 10, t.v.) resemble very much the tori semi- 
circulares in structure. The sides forming the walls of the fissure constituting the 
posterior part of the fourth ventricle are lined by a layer of connective tissue bounded 
internally by a single row of epithelial cells, precisely in the same way that the 
surface of the torus facing the ventricle of the optic lobe is covered. A vertical row 
of cells is placed externally to this ependyma of the same kind as those found beneath 
that structure in the torus. The only difference that exists between these two 
tuberosities is, that in the one belonging to the vagus the groups of cells project more 
beyond the level of the nervous tissue into the ependyma than in the torus, and also 
that the larger cells which exist in the latter are not found in the former. That part 
of the medulla oblongata which bridges over the narrow part of the fourth ventricle 
consists entirely of granular matter, and no cells of any kind are to be seen in it. 
Transverse Commissures of .the Central Nervous System. 
In the anterior part of the spinal cord only two commissures are visible — one about 
half way between the central canal and the ventral edge of the cord ; this is the 
ventral commissure (fig. 1 , v.t.c.) which connects the ventral horns of grey matter of 
the two sides. The other is visible only in sections which pass through the dorsal 
roots of the nerves, and connects the dorsal horns of grey matter of the two sides. 
This latter commissure is more pronounced nearer the fourth ventricle, and immediately 
behind the fissure of the medulla oblongata it comes to be closely applied to the dorsal 
edge of the central canal. 
The two commissures mentioned by Mauthner (50) are not visible in Mugil ; the 
place which he indicates for them being occupied in this species by connective tissue : 
the “ substantia gelatinosa centralis u of Stilling. This connective tissue is composed 
of fibres derived from the epithelial layer surrounding the central canal of the cord. 
Immediately behind the posterior fissure of the fourth ventricle a series of trans- 
verse commissures come to view, which gradually take the place of the ventral com- 
missures of the cord, although they do not occupy exactly the same relative position. 
They connect the tuberosities of the vagi together and increase in size, pari passu, 
with the latter ; they pass downward and across to the other side ventrad of the 
central longitudinal column. 
At about the middle of the vagus territory they unite the root of one nerve to that 
of the other. At this point one of the branches of the above-mentioned commissures 
turns back at the clorso-exterior angle of the tuberosity of the vagus, passes downward 
