I02 A MANUAL OF ANATOMY 



where they he in the intermaxillary suture. These are known 

 as the foramina of Scarpa, and they transmit the naso-palatine 

 nerves, the left nerve passing through the anterior, which usually 

 communicates with the left nasal fossa, and the right through 

 the posterior, which usually communicates with the right nasal 

 fossa. The other two foramina are situated one at either side, 

 and are known as the foramina of Stensen, and the canal into which 

 each leads opens superiorly on the floor of the corresponding nasal 

 fossa, close to the outer side of the incisor crest. Each of Stensen's 

 canals transmits a branch of the superior or descending palatine 

 artery from the anterior palatine fossa to the nasal fossa. The 

 inner wall of Stensen's canal, on each side, represents the mesial 

 palatal process of the premaxilla or intermaxillary bone, and also 

 a portion developed from the prepalatine centre. The canals of 

 Stensen correspond to the incisor foramina of many animals — 

 e.g., the ruminantia, in which they are of large size, and each opens 

 independently on the front part of the hard palate as a large aper- 

 ture, there being no anterior palatine fossa. In such animals each 

 incisor foramen leads up to the orifice of Jacobson's organ, which 

 is a supplementary organ of smell. In man the canals of Stensen 

 are the remains of a communication which existed in early foetal 

 life between the nasal and buccal cavities. 



Passing transversely outwards from the anterior palatine fossa 

 at its back part to the interval between the lateral incisor and 

 canine teeth a suture is always present in early life, and may 

 persist in the adult, which indicates the line of junction of the 

 maxillary portion proper and the premaxilla or intermaxillary bone, 

 the latter representing the part which bears the central and lateral 

 incisor teeth. This intermaxillary portion forms an independent 

 bone in many animals. 



The antrum of Highmore or maxillary air sinus is situated 

 within the body of the bone, and is of large size, its capacity in 

 health being equal to about 2 drachms. It has the shape of a 

 four-sided pyramid, and is lined with mucous membrane continuous 

 with that of the nasal fossa. The apex corresponds to the malar 

 process, and the base represents the internal or nasal aspect. The 

 superior wall or roof is formed by the orbital plate. The inferior 

 wall or floor is formed by that portion of the alveolar border which 

 contains the molar and second bicuspid alveoli, and, in some cases, 

 the first bicuspid alveolus also. It is often very irregular, due tc 

 projections of the upper ends of the alveoli, and in some cases the 

 root of the first molar, and, it may be, that of the second, projects 

 into the antral cavity. The ant ero- external wall is formed by the 

 facial surface, and is thin and translucent over the region of the 

 canine fossa. It contains the anterior, and the lower part of the 

 middle, dental canals. The postero- external wall is formed by the 

 zygomatic surface, and it contains the upper part of the middle 

 dental canal. The opening of the antrum, which is large and 

 irregular, is situated on the base or nasal aspect. In the articu- 



