48 ABNORMAL CONDITIONS OF THE AXIS. 



187. The head of a foetal Pig with entire deficiency of the facial 



axis, naso-frontal processes, and eyes. There is a V-shaped 

 fissure in the position of the eyelids, which has been en- 

 larged on the right side to show the complete deficiency 

 of the eye. The skull has been opened above, and the 

 cerebellum is seen to be the only portion of the brain it 

 contains. Mus. Brit. 



188. A portion of the occipital and parietal bones of the same. 



Mus. Brit. 



189. The head of a foetal Pig with anterior deficiency of the 



facial axis and absence of the eyes. The maxillary pro- 

 cesses are separated by a deep wide fissure, so that the 

 two halves of the snout are turned outwards and upwards. 



Hunterian. 



C. Mesencephalic arrest. 

 Syn. Anopia. 



It sometimes happens that the middle of the cranial axis and 

 cavity are deficient, whilst the anterior cerebral lobes and the 

 anterior facial region are normal. In this condition the eyes 

 are rudimentary or absent. The tentorium divides the cranial 

 cavity, sometimes to such an extent as entirely to separate the 

 cerebral hemispheres from the cerebellum. 



190. A vertical longitudinal section of the head of a Lamb, in 



which the cerebellum is cut off from the cerebrum by the 

 tentorium. The axial parts between the cerebrum and 

 cerebellum are entirely wanting. The eye is very small 

 and rudimentary. There is atresia of the oesophagus, the 

 upper part of which is apparently entirely wanting. The 

 pharynx is wanting and the mouth ends in a pouch behind 

 the tongue. 



191. Half the skull of the same. The bones are all present but 



the orbito-sphenoids, which are represented by membrane 

 only. The frontals are much elevated in front and de- 

 fective behind; the parietals and all the bones behind 

 the frontals are very small. The eye on this side was 

 exactly like that on the other. 



D. Epencephalic arrest. 



The axis of the skull immediately in front of or between the 



