42 SPHENOID BONE. 



Upon the antero-inferior surface is a long flattened spine, the 

 rostrum, which articulates with the vomer ; and on each side of the 



rostrum an irregular opening, 

 I?* leading into the sphenoidal 



cells : these openings are par- 

 tially closed by two thin plates 

 of bone (frequently broken 

 away), the sphenoidal spongy 

 bones. On each side of the 

 sphenoidal cells are the out- 

 lets of the optic foramina, 

 sphenoidal fissures, and fora- 

 mina rotunda, the lesser and 

 greater wings; and below, 

 the pterygoid processes. 



Upon the under surface of the body are two small fissures^con-^ 

 verted into canals by the vomer, the pterygo-palatine canals, which 

 transmit the pterygo-palatine arteries ; and traversing the roots of 

 the pterygoid at their union with the body, two pterygoid or Vidian 

 canals, which give passage to the Vidian nerve and artery at each 

 side. The posterior surface is flat and rough, and articulates with 

 the basilar process of the occipital bone. In the adult this union is 

 usually completed by bone; from which circumstance the sphenoid, 

 in conjunction with the occipital, was described by Soemmering 

 and Meckel as a single bone, under the name of spheno-occipital or 

 basilar bone. This surface is continuous on each side with the 

 spinous process, and at the angle of union is the termination of the 

 Vidian canal or foramen ptefygoideum. 



The lesser wings (processes of Ingrassias) are thin and triangular, 

 the base being attached to the upper and anterior part of the body 

 of the sphenoid, and the apex extended outwards, and terminating 

 in an acute point. The anterior border is irregularly serrated, ihe 

 posterior being free and rounded, and received into the fissure of 

 Sylvius of the cerebrum. The inner extremity of this border forms 

 the anterior clinoid process, which is supported by a short pillar of 

 bone, giving attachment to a part of the common tendon of the 

 muscles of the orbit. The lesser wing forms the posterior part of 

 the roof of the orbit, and its base is traversed by the optic foramen. 

 The greater wings present three surfaces ; a superior or cerebral, 

 which forms part of the middle fossa of the base of the skull, an 



* The antero-inferior view of the sphenoid bone. 1. The ethmoid spine. 2. The 

 rostrum. 3. The sphenoidal spongy bone, partly closing the left opening 1 of the sphe- 

 noidal cells. t 4. The lesser wing. 5. The foramen opticum piercing the base of the 

 lesser wing. 6. The sphenoidal fissure. 7. The foramen rotundum. 8. The orbital 

 surface of the greater wing. 9. Its temporal surface. 10. The pterygoid ridge. 

 11. The pterygo-palatine canal. 12. The foramen of entrance to the Vidian canal. 

 13. The internal pterygoid plate. 14. The hamular process. 15. The external 

 pterygoid plate. 16. The foramen spinosmn. 17. The foramen ovale. 18. The 

 extremity of the spinous process of the sphenoid. 



t This is a part of the pyramid of Wistar. See description of ethmoid. 



