The Brain 



291 



The Brain. 



The brain commences to form and is recognizable before the 

 neural canal has been completed. It consists at first chiefly of a 

 series of vesicles which are known as the fore-brain, mid-brain, 

 and hind-brain. The anterior cerebral vesicle, or fore-brain, gives 

 rise very early in its development to the optic vesicles, as lateral 

 outgrowths, which are ultimately converted into the essential 

 parts of the eye. 



Normalh', there are two of these outgrowths, which, under 

 aberration in development, may fuse or grow out as single pro- 

 jections on the median line, to constitute the one-eyed monster, 



MP 



4- SM 



IM 



Fig. 29. Skull of Cyclops. I'oal. 



Oc, Occiput. O, Single orbital cavity. 



MP, Coronoid process of inferior maxilla. 



SM, Superior grinders. 



SI, Superior incisors fused into a single organ. 



IM, Inferior grinders. T, Tongue. 



11, Inferior incisors. 



