OS FBONTIS. 



61 



fications from different nuclei, where these original mem- 

 braneous septa do not exist, a suture will not be formed ; but 

 the bones will join each other, as in a case of callus between 

 the broken extremities of bones. When these septa become 

 weak or thin, either from original tendency, as in the case of 

 the sagittal suture, which in early life is continued to the root 

 of the nose frequently ; or from advanced age, as in the case 

 of nearly all sutures, the bones of the opposite sides amalga- 

 mate, and no appearance of suture is left. It is easy to make a 

 preparation illustrative of these facts, and one now exists in 

 the museum of the University of Pennsylvania, in which, by 

 removing the bone from between the membranes by means of 

 an acid, and afterwards rendering the membranes transparent 

 with oil of turpentine, the septa are seen sufficiently distinctly.] 



Os Frontis. 



The OS frontis, as its name imports, forms the front part of 

 the cranium, and the upper portion of the orbits of the eyes. 



Fig. 10.* The external surface of this 



bone is smooth at its upper 

 convex part ; but several pro- 

 cesses and cavities are ob- 

 servable below ; for at the 

 angles of each orbit, the 

 bone projects to form four 

 processes, two internal, and 

 as many external ; which are 

 denominated angular. Be- 

 tween the internal and exter- 

 nal angular processes on each 

 side, an arched ridge is ex- 



* The external surface of the os frontis. 1. Frontal protuberance or boss of 

 the right side. 2. The superciliary ridge. 3', Supra-orbital ridge. 4. External 

 angular process. 5. Internal angular process. 6. Supra-orbital notch for the 

 transmission of the supra-orbital nerve and artery ; it is occasionally converted 

 into a foramen. 7. The nasal or superciliary boss ; the swelling around this 

 point denotes the situation of the frontal sinuses. 8. The temporal ridge, com- 

 mencing from the external angular process (4). The depression in which fig. 

 8 is situated is a part of the temporal fossa. 9. The nasal spine. 



