50 ABNORMAL CONDITIONS OF THE AXIS. 



bent at right angles to the cranial axis, and the cribriform plate 

 forms part of the floor of the brain-case, the whole brain being 

 pressed forward by the contraction of the posterior portion of the 

 skull. 



In cases of this character the ethmoid bone and nasal capsule 

 are also often deficient. These form a connecting link between 

 epencephalic and prostho-epencephalic arrest. \ 



194. A longitudinal vertical section of the head of a foetal Lamb, 



with deficiency of the lower jaw and mouth. The bullse 

 of the ears and malar bones are fused beneath. The facial 

 and cranial axis are in the same line. The median struc- 

 tures of the brain are all more or less defective behind, 

 and the lateral halves are fused in the median line. The 

 cerebral hemispheres, corpus callosum, and fornix are 

 normal. The eyes were approximated and directed down- 

 wards. The pharynx has not been preserved, but was 

 probably similar to that in the following preparations. 



Presented by Sir E. Home, Bart. 



195. The skeleton of the other half of the same head. The fusion 



of the squamosal bones, zygoma, malar, and superior max- 

 illary bones across the mesial line below is well seen. The 

 basisphenoid and presphenoid bones are absent, and the 

 basioccipital is narrowed in front. 



Presented by Sir E. Home, Bart. 



196. The head and neck of a foetal Lamb, with deficiency of the 



mandible and fusion of the ears. The facial is at right 

 angles to the cranial axis, so that the ethmoid forms part 

 of the floor of the skull-case. 



The side of the skull has been partially removed to show the 

 base from within. A section has been made through the nasal 

 cavity, and the pharynx has been laid open. A purple glass rod 

 marks each of the following : The optic foramina, foramina ro- 

 tunda, and the tongue, a hollow organ situated above the anterior 

 part of the pharynx. The only external opening of the pharynx 

 is hy the Eustachian tubes and external auditory meatuses. The 

 memhrana tympani were absent. Blue glass rods mark the sphe- 

 noidal fissure, the foramen ovale, the external auditory meatus, 

 and the anterior condyloid foramen. A white rod has been placed 

 in the jugular foramen. 



Hunterian. 



