64 



THE BONES. 



Fig. 35. 



cevebellnm ; and for this purpose it shows four foss^, distinguished into superior or 



cerebral, and inferior or cerebellar. These foss« are separated by a crucial projection 



■whose most developed portion forms the internal occipital protuberance. 



The union of the occipital with the parietal bones constitutes the lambdoidal suture. 



At the point where this bone meets the parietal and the squamous portion of the 



temporal, is found, in the infant, the lateral posterior fontanella. 



2. Parietal hones.— The parietals are always isolated in early life, and sometimes 



consolidated with each other at the adult age. They are very large, quadrilateral, and 



occupy the summit and sides of the cranium. 



The parietal crests are absent, but are replaced, 

 in certain individuals, by two faintly-marked 

 curved lines situated a little above the inferior 

 border of the bone. The middle portion of the 

 external face is very convex. 



On the internal face there is no parietal pro- 

 tuberance, but in its stead the internal occipital 

 protuberance. It also exhibits ramous channels, 

 which in disposition are analogous to the ribs of 

 a tig-leaf ; as well as the parietal fossa which cor- 

 responds to the parietal eminence. 



X Frontal fcoiie.— The frontal bone of Man forms 

 the upper part of the face and the anterior portion 

 of the cranium. Convex from behind forward, then 

 vertical in its upper three-fourths, the bone sud- 

 denly bends at the orbits, so as to become hori- 

 zontal in its lower fourth. 



The external face offers, above the forehead, two 

 lateral frontal eminences, and above the nose, a 

 middle frontal boss. To the right and left of the 

 latter are two salient arches, the supraorbital ridges. 

 The internal face entirely belongs to the cranial 

 cavity. It offers on the median line, the saggital 

 groove terminated by a frontal crest ; and on each 

 side of this line the frontal fossse, corresponding 

 to the eminences of that name, and orbital bosses 

 to match the orbital roofs. There is no mortice for 

 the articulation of the sphenoid bone. 



On the middle portion of the superior frontal 



border, in young persons, is the anterior angle of 



Lachrymal fossa ; 8, Opening of the anterior fontanella. The anterior border ex- 



FEONT VIEW OF THE HDMAN 

 CRANIDM. 



1, Frontal bone ; 2, Nasal tuberosity ; 

 3, Supra-orbital ridge ; 4, Optic 

 foramen ; 5, Sphenoidal fissure ; 

 6, Spheno-maxillary fissure ; 7, 



the nose divided by the vomer ; 9, 

 Infra-orbital foramen; 10, Malar 

 bone; 11, Symphysis of the lower 

 jaw; 12, Mental foramen; 13, 

 Ramus of the lower jaw; 14, Parie- 

 tal bone; 15, Coronal suture; 16, 

 Temporal bone; 17, Squamous 



hibits three superciliary foramina and the orbital 

 arches. 



4. Ethmoid hone. — In Man, the external face of 

 the lateral masses, formed by a very thin lamina, 

 termed the os planum or lamina papyrac^, belongs 

 to the internal wall of the orbit. 



5. Sphenoid hone. — This is distinguished, in 

 suture; 18, Upper part of the great Man, into a body and four wings, two large and 

 ala of the sphenoid bone ; 19, Com- two small. 



The inferior surface of the body offers nothing 

 remarkable, except the presence of a conical pro- 

 longation named the beak (rostrum) of the sphe- 

 noid. The external face of the greater wings forms 

 part of the temporal fossa, as also the external wall 

 of the orbit At the union of the wings with the body are detached two biiid ptery- 

 goid processes ; their internal branch represents the pterygoid bones of animals. There 

 is no subsphenoidal canal. 



The two lesser wings are very thin and triangular, and visible only on the superior sur- 

 fece of the bone; they constitute the processes of Ingrassias. 



On the internal face of the bone are found : — 1, A deep pituitary fossa, limited by 

 four clinoid processes : 2, An optic fossa, shallow, showing very short optic canals trans- 

 formed into foramina: 3, The sphenoidal fissure, which replaces the great super- 

 sphenoidal canal in the Horse; 4, The great foramen rotundum : 5, The internal face of 

 the wings, much excavated ; 6, The foramen ovale, which transmits the inferior maxillary 

 nerve; 7, The small foramen rotundum that lodges the spheno-spiuous artery. 



mencement of the temporal ridge; 

 20, Zygoma of the temporal bone, 

 concurring to form the temporal 

 arch ; 21, Mastoid process. 



