A CASE OF CYCLOPIA 239 



tween the approximated walls and finally by complete obliter- 

 ation of the ependyma. Such an explanation is however purely 

 theoretical, as there is no way of determining the time relation 

 between the onset of hydrocephalus and the occlusion of the 

 anterior portion of the third ventricle. 



REVIEW OF CASE REPORTED BY O. NAEGELI 



In the case reported by Naegeli (17) the cerebrum was repre- 

 sented by an unpaired, thick walled vesicle, having a very slight 

 attachment to the massive thalamus. 



The basal ganglia were quite defective and could not be defi- 

 nitely identified. He described, however, a thin plate of embryonic 

 cells in the region of junction between the thalamus and cerebrum 

 which he concludes may represent these structures. 



No olfactory bulb or stalk was present but he describes the 

 hippocampal formation as being well developed, and the fimbria 

 as containing medullated fibers. In figure 29 of his report he 

 shows the cornu ammonis in transverse section and it is strikingly 

 similar to sections through this region in the present case. Un- 

 fortunately, he has not described the relations of the hippocam- 

 pus except to mention that it is a distinctly paired formation, 

 so further comparison is impossible. The fornix is also mentioned 

 as an unpaired bundle which divides into symmetrical halves to 

 end in the region of the corpora mammillaria. The relations 

 of this fornix to the fimbriae are not clear. 



The cortex of the cerebral vesicle showed a distinctly laminated 

 arrangement of its cells and was quite markedly thicker than 

 normal — the greatest increase in thickness being in the deep or 

 polymorphic stratum. In figure 42 of his report he shows a 

 carmine stained section through the cerebral cortex, in which 

 the cell lamination is almost precisely the same as that described 

 as appearing under low magnifications in the present case. He 

 also found a few poorly medullated radial fibers in the layer of 

 large pyramidal cells. No tangential fibers were present. 



The thalamus was massive and of nearly normal form, but 

 the two halves were strongly fused in the mid-line ventrally. 



