1885.] 



OF THE HUMAN SPHENOID BONE. 



581 



The details of the ossification of the presphenoid, or that portion 

 in relation with the optic nerves, may he summarized as follows : — 



Fig. 3. 



p.s. 



O.F. 



0.S. 



P. F. 



A series of figures to show the disposition of the various nuclei of the human 



sphenoid bone. 



The upper figure shows the relation of the centres to the cartilage; the 



latter in all cases is represented by dots. 

 In the middle figure the basisphenoidal nuclei have coalesced, the orbito- 



sphenoids have joined the prespheiioids, and the internal pterygoids 



have joined the alisphenoids. 

 In the lowest figure the sphenoid bone is represented as at the eighth 



month of foetal life. 



.^.S, Ali sphenoid ; -B.S, basisphenoid; i, lingulae; i?'. pterygoids ; O.-S, orbito- 

 sphenoids; P.S, presphenoid ; Ci*^, oxatio foramen ; /*'./?, foramen rotun- 

 dum ; F. 0, foramen ovale ; C, cranio-pharyngeal canal. 

 The dorsum sellse at this date is cartilaginous, and therefore it is not repre- 

 sented in the figures. The foramen ovale, until some time after birth, is only 

 a notch in the alisphenoid. 



Ossific matter is deposited immediately external to the optic foramen, 

 and extends rapidly outwards to form the orbitosphenoid. This 

 occurs about the commencement of the third month. 

 Proc. Zool. Soc— 18S5, No. XXXVIII. 38 



