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tlie whole of its lower edge which is bevelled at its inner part, so that it 

 is covered by the alse minores of the os sphenoides, which is shaped ob- 

 liquely at the outer part of the bone. The frontal bone is articulated, be- 

 sides, with the lateral and inferior parts of its upper edge. The remain- 

 der of this upper part is united to the anterior edge of the parietal bones, 

 which by means of a slope, in a different direction, rest on the middle 

 part of this edge, while the frontal bone is applied to them laterally. 



This bone which the effort tends to force upward and backward, can- 

 not yield to this double impulse, for, on the one hand, its mode of articu- 

 lation with the anterior edge of the alae minores of the sphenoidal bone, 

 and the internal -part of the anterior edge of the parietal bones, resist 

 this tendency upward, while the resistance from the latter, prevents them 

 from being forced backward. That share of the effort which affects the 

 parietal bones, follows the curved lines described by these bones, and ex- 

 tends along that formed by the occipital, and thus reaches the posterior 

 face of the body of the sphenoid bone. 



The portion directly transmitted by the anterior and inferior face of 

 this bone, by the ossa palati and by the vomer, is considerable and pro- 

 portioned to their thinness. The anterior half of the body of the sphe- 

 noid bone, hollowed by the sphenoidal sinus, would have been incapable 

 of supporting greater pressure. Lastly, the situation of the body, placed 

 between the dental arches, in front of the place occupied by the ossa pa- 

 lati, explains why this transmission is chiefly effected by the upper maxil- 

 lary bones. 



The above is the manner in which the effort exerted from below up- 

 ward, by the lower on the upper jaw, is carried to the anterior, posterior, 

 and inferior faces of the body of the sphenoid bone. 



The temporal bones which are affected by it, in a very slight degree, 

 by means of the zygomatic processes of the malar bones, support the 

 greater weight of the effort acting from above downward, or from the 

 arch of the skull towards its base. The weight laid on the head, tends 

 to depress or to separate the parietal bones, which resist the pressure, in 

 consequence of the support afforded them by the temporals. These trans- 

 mit the effort to the lateral and posterior parts of the body of the sphe- 

 noid, by means of the alae majores of that bone, which are articulated, along 

 the whole extent of their external edge, and along the posterior fourth of 

 their internal edge, with the temporals. Besides, the upper extremity of 

 the alae majores is sloped, on the inner part of the bone, that it may be ar- 

 ticulated with the anterior and inferior angles of the parietal bones, and 

 answer the same purpose to them as the squamous portion of the tem- 

 porals. 



The lateral and posterior parts of the body of the sphenoid support, 

 therefore, almost the whole effort of the pressure applied to the parietal 

 bones. It is communicated to them by the ate majores, which receive 

 it themselves, either directly at the anterior and inferior angles of this 

 bone, or through the medium of the temporals. The small portion of 

 the effort transmitted by the latter to the occipital, follows the curved 

 line of this bone, and is felt on the posterior face of the body of the sphe- 

 noid. 



To the effort resulting from the pressure exerted by the body on the 

 summit of the head, one should add that occasioned by the contraction of 

 the muscles which elevate the lower jaw. These tend to depress the tem- 

 poral, the malar and the sphenoid bones, and in this action, they employ- 



