580 MR. J. B. SUTTON ON THE DEVELOPMENT [Juiie 2, 



central canal of the encephalic vesicles turning round the most 

 anterior end of the notochord in tlie form of an infundibulum, to 

 form a continuity with the buccal epiblast and come in very close 

 relationsliip at first with the extreme end of the foregut ; the place 

 where these highly interesting occurrences take place being for a 

 long time represented by the cranio-pharyngeal canal. The inquiry 

 needed to malce the demonstration complete is, to determine 



rig. 2. 



The posterior wall of the pharynx, showing the position of the Bursa pharyngea, 

 B.P. From a foetus at the fifth month. 



positively whether the infundibulum is always a cul-de-sac, or at 

 some period communicates with the cavity of the future pharynx. 



It is a very remarkable fact that the pituitary fossa and the space 

 between the bladder and the rectum are common situations for 

 those curious tumours known as leratomata; it will be interesting 

 to ascertain tiie relation of the curious neurenteric passages to these 

 morbid growths. 



The ossification of the sphenoid must now be considered. 



The alffi arise from single nuclei in the cartilage forming the 

 lateral walls of the skull immediately anterior to the periotic cartilage, 

 commencing about the eighth week of intra-uterine life. They are 

 t!ie first centres of this important bone to make an appearance. 



A little later two circular spots may be detected in the cartilage 

 forming the floor of the pituitary fossa. They first become visible 

 on the under surface of the bone, and are not affected when the peri- 

 chondrium is removed : these are the paired basisphenoidal nuclei. 



They are very quickly followed by two earthy spots in the 

 lingulse, lying between the alse and basisphenoidal nuclei, as shown 

 in fig. 3 A, which represents the disposition of these six nuclei, three 

 on either side, viz. basi-, lingulae-, and alisphenoid centres. 



The two for the basisphenoid become quickly confluent from below 

 upwards, and the lingulse soon fuse with them and form a porous 

 mass. The alse grow rapidly, but remain separated from the lingulse 

 b}' a thin layer of cartilage until the first year after birth. 



These six centres constitute with the internal pterygoid plate, 

 which will be considered further on, the posterior portion of the 

 sphenoid bone. 



