A CASE OF CYCLOPIA 



211 



As has been noted, the basal portion of the cerebrum, which 

 posteriorly is more or less bilaterally symmetrical, is separated 

 from the cerebellum bj^ a very deep fossa. 



From above on removal of the roof: On laying back the smooth, 

 thin, arched roof, a cavity is brought to view which repre- 

 sents the dilated ventricular cavitA^ of the primary forebrain. 

 The floor of this cavity, which is quite vascular, is seen in figure 

 51 to be marked by a Y-shaped ridge which corresponds to the 

 external furrow before mentioned. Overhanging somewhat the 

 basal limb of this Y-shaped ridge posteriorly there is seen a smooth 

 rounded protuberance of more or less pyriform outline. Sub- 

 sequent examination has shown this to represent the only per- 

 sisting portions of the thalamus. At its base this thalamic mass 

 becomes flattened from within outward, and is continuous with 

 the thickened basal portion of the cerebrum as seen in the dia- 

 gram of the brain in sagittal section (fig. 11). 



Cor. pin. C.hb 

 C.p. 



Vent.m- 



Vent.lV 



Nu.o.i 



Cor.cer. 



Fig. 13 



Fig. 12 



Fig. 11 Diagrammatic medial sagittal section through the entire brain. The 

 levels at which the following coronal sections (figs. 12 and 13) were taken are 

 indicated. Aq.c, iter; C.hb., habenular commissure; Cor.cer., cortex cerebri; 

 Cor. pin., pineal body; C.-p., posterior commissure; N.IV., trochlear nerve; Nu.o.i,. 

 inferior olive; Nu.r., red nucleus; P., pons; Rad.th., ventral thalamic radiations; 

 T.c, taenia cerebri, or point of attachment of thin cerebral roof (Epij) to inner 

 pillar of cerebral margin; Tec.Mes., midbrain roof; Th.D., dorsal thalamic mass; 

 T.th.I., attachment of cerebral roof to thalamus; T.th.III., attachment of thin 

 roof of third ventricle to thalamus; Vent.I., cerebral ventrijle; Vent. III., third 

 ventricle; Vent.I]"., fourth ventricle; A'., ependymal diverticulum from iter. X|. 



