90 OSSA UNGUIS. 



at the root of the nose. They are each of an irregular oblong 

 figure, being broadest at their lower end, narrowest near the 

 middle, and larger again at the top, where the edge is rough 

 and thick, and their connexion with the os frontis is conse- 

 quently very strong. They are convex externally, and concave 

 within. The lower edges of these bones are thin and irregular. 

 Their anterior edges are thick, and their connection with each 

 other, by means of their edges, is firm ; the suture between 

 them, extending down the middle of the nose, forms a promi- 

 nent line on the internal surface, by which they are united to 

 the septum narium. The uppermost half of their posterior 

 edges is covered by the edges of the nasal processes of the 

 upper maxillary bones ; the lower half laps over the edges of 

 these bones ; and by this structure they are enabled to resist 

 pressure. [On the posterior surface of the os nasi is a groove 

 occupied in the recent subject by a branch of the ophthalmic 

 nerve called the nasal, which enters the nose through the fora- 

 men orbitare internum anterius.] They are joined above to the 

 OS frontis; before, to each other; behind, to the upper maxillary 

 bones ; below, to the cartilages ; and internally, to the septum of 

 the nose. 



Ossa Unguis, or Ossa Lachrymalia. 



The ossa unguis are so named from their resemblance to a 

 nail of the finger. They are situated on the internal side of the 

 orbit of the eye, between the os planum of the ethmoid, and 

 the nasal process of the upper maxillary bone. Their external 

 surface is divided into two portions, by a middle ridge ; the 

 posterior portion forms part of the orbit ; and the anterior, which 

 is very concave, forms part of the fossa and canal, for contain- 

 ing the lachrymal sac and duct. This portion is perforated 

 by many small foramina ; and the whole, being extremely thin 

 and brittle, is therefore often destroyed by the preparation of the 

 subject. 



The internal surface of this bone is generally in contact with 

 the cells of the ethmoid ; a small portion of the anterior parts is 

 in the general cavity of the nose. Each os unguis is joined 



