444 
four regular recti muscles. Part of these muscle slips are innervated 
by the branches from the fourth nerve, while some in the external 
region receive branches from the maxillary branch of the fifth. 
The brain. The primary forebrain when floated in a fluid is an 
undivided sac that is quite symmetrical in outline, Figs. 5—6. There 
are no ridges or sulci on the dorsal or lateral surfaces. In the anterior 
ventral surface a single distinct lobe is present that apparently is the 

Fig. 5. Fig. 6. 
Fig. 5. Dorsal viev of cyclopian pig brain. C. qu. Corpora quadrigemiua. 
Th. ma. Thalmic mass. . 
Fig. 6. Ventral viev of cyclopian pig brain. JJ, IV, V, etc., cranial nerves. 
undivided olfactory lobe, Fig. 6. Seen from the side, the roof of the 
primary forebrain is in contact with the floor, Fig. 7. A roundish 
body shows through the thin membranous roof that is the thalmie 
mass, Figs. 5, 7. Immediately posterior are the two anterior corpora 
quadrigemina. The posterior pair are small and lateral in position. 
