742 
MR. A. SANDERS ON THE ANATOMY OF THE 
Most of the authors in the list, homologised these bodies with the corpora 
albican tia. Carus (12) was the first to compare them to the tuber cinereum, 
with which part they agree in position. Serres and Leuret also adopted this 
view, but Klaatsch confined this interpretation to the slight eminence (the trigonum 
fissum) to which the hypophysis is attached. Cuvier termed them “lobes optiques;” 
Mayer compared them to the thalamus opticus and corpus striatum combined ; while 
Hollard (55) homologised them to the corpora striata, because, as he pointed out, 
the fibres which correspond, as he supposed, to the corona radiataof the cerebrum pass 
into them to end there ; but this fact was denied by Yulpian (56), who stated that 
these fibres pass through them without terminating, and go on into the medulla 
oblongata. This, I think, is most probably an error. 
Girgensohn (42) emitted the curious opinion that these bodies were together a 
highly developed hypophysis : an opinion which is evidently based on the supposition 
that the latter is composed of nervous tissue. In many fishes the hypophysis is easily 
broken off, and does not remain attached to the brain when the latter is removed 
from the skull ; in that case, a small fissure is seen on the trigonum from which it is 
torn, which is the lower opening of the infundibulum. 
There is no apparent line of separation between the medulla oblongata and the 
spinal cord, the latter gradually passing into the former ; but the posterior end of 
the vagal tuberosities may be taken as a landmark for want of a better. 
The anterior part of the spinal cord (fig. 14) has somewhat of a four-sided figure 
with the angles cut off ; the dorsal and the ventral fissures are represented only by 
shallow depressions, the dorsal one becoming deeper on approaching the posterior end 
of the medulla oblongata. At this part the central canal has an oval section, the long 
axis of which is placed at right angles to the long axis of the cord. This canal 
(c.ca., fig. 14) becomes smaller at a point nearer the fourth ventricle and also circular 
in outline ; it then enlarges in a funnel-shaped manner, and becoming notched on its 
upper margin joins the gradually deepening dorsal fissure and enters the posterior 
section of the fourth ventricle. Occasionally a rod is seen in sections through this 
central canal of the cord, which most probably is the coagulated liquid contained 
therein, as Stieda suggested ; it is only in a few sections that this rod is seen, for it 
usually falls out, not being retained in its place by any attachments. 
The fourth ventricle (fig. 10, s.r.) consists of two separate portions ; the posterior 
part is a deep trench, situated between the two lobes of the vagus, the walls of which 
are nearly perpendicular and the floor rounded. Superiorly, this trench is covered by 
a layer of pia mater which passes over from one tuberosity to the other. Anteriorly, it 
passes by means of a quadrangular passage into the main part of the ventricle (fig. 9, 
s.r.), which is a wide space beneath the cerebellum and between the crura thereof 
(fig. 10). The passage between the two divisions of this ventricle is formed by a bridge 
of nervous tissue, which in some species'"' becomes enlarged into a tuberosity. Before 
* Carp family. 
