HEAD AND NECK IN SECTION 15 



placed one on either side of the middle line above the entrance to the 

 oesophagus. These bulgings are caused by the pressure on the pharyngeal 

 wall, of the anterior diverticula of the guttural pouches. The inner wall 

 of one of the pouches, namely, the right, is distinctly shown in the 

 plate, since in this case the operator whilst making the section was 

 fortunate enough to strike the median line, and so preserved the 

 walls of the pouches intact. It will be observed that the pouch is 

 elongated from before backwards, and that it also presents a posterior 

 diverticulum which extends downwards," backwards and outwards 

 towards the angle of the inferior maxillary bone. 



Above the pharynx part of the perpendicular plate of the ethmoid 

 bone is visible, as are also some of the ethmoidal cells, which are 

 attached to the anterior aspect of the horizontal or cribriform plate of 

 the ethmoid. At a still higher level the opening of the right frontal 

 sinus is placed. The septum between the two sinuses was present after 

 the section was made, but has been removed in order that the interior of 

 the sinus may be brought into view. 



Running downwards and forwards (in the ordinary position ot the 

 head downwards and backwards) from the bodv of the frontal bone, we 

 have the reflected plate of that bone which bounds the frontal sinus, and 

 which is articulated inferiorly to the horizontal plate of the ethmoid. 

 This reflected plate is the partition which separates the frontal sinus from 

 the cranial cavity, and it forms a very acute angle with the body of the 

 bone to which it is attached, the apex of the angle being directed 

 upwards, and thus it is that the frontal sinus ascends some distance 

 above and in front of the lower boundary of the cranial cavity. 



The inner aspect of the right cerebral hemisphere is observed 

 since the falx cerebri has been removed, while the corpus callosum 

 which united the two hemispheres is seen to have been cut through. 

 Extending downwards and forwards from the posterior extremity of 

 the corpus callosum is the fornix. 



Posteriorly in the cranial cavity we notice a section through the 



