40 ABNORMAL CONDITIONS OF THE AXIS. 



yond the anterior extremity of the truncated skull. The 

 cranium and part of the spinal canal has been laid open. 

 The four anterior ganglia are much compressed from 

 before backwards. The anterior pair (olfactory) have 

 displaced the second pair, the cerebral hemispheres, and 

 lie partially between instead of entirely in front of them. 



141. The head of a young Salmon with a similar truncated face; 



the maxillse are placed almost at right angles to their 



normal position, and lap over the mandible on either side. 



Presented by Mr. Shepherd, 1871. 



142. A vertical longitudinal section of the anterior part of a Carp, 



with complete deficiency of the face in front of the eyes. 

 The development of the mandible is likewise defective ; 

 it does not extend beyond the truncated face. 



Hunterian. 



IN BIRDS. 



143. A Sparrow with a' deep cleft dividing the mandible and 



lower beak in the mesial line. Hunterian. 



144. A fcetal Chick in which the anterior portion of the cranio- 



facial axis is absent. The eyes are fused into a single 

 organ. The upper beak and the maxillary and frontal 

 arches are entirely wanting. Purchased. 



IN MAMMALS. 



A. Facial arrest. 



Facial arrest in its slightest degree consists in arrested deve- 

 lopment of the intermaxillaries and maxillary bones, so that a 

 cleft is left between them, constituting cleft palate or Hare-lip. 

 The nasal septum is defective in the more severe forms, or the 

 whole anterior part of the axis, including the ethmoid bone, may 

 be deficient. All the facial bones may be very defective, with 

 shortening of the bones of the base of the skull. Very frequently 

 this shortening appears to be accompanied by an increase of 

 breadth in the axial bones, giving rise to considerable clefts be- 

 tween the arrested parts of the face. 



145. A portion of the skull of a six-months* foetus with consi- 



derable deficiency of the maxillae and palate-bones, giving 

 rise to a wide cleft in the palate. The vomer supports 



