122 SPECIAL ANATOMY OF THE SKELETON 



The sphenoparietal (sutura sphenoparietalis) is very short; it is formed by the 

 tip of the greater wing of the sphenoid, which overlaps the anterior inferior angle 

 of the parietal bone. 



The squamoparietal (sutura squamosa) is arched, and is formed by the squamous 

 portion of the temporal bone overlapping the middle division of the lower border 

 of the parietal. 



The mastoparietal (sutura par ietomasto idea), a short suture, deeply dentated, 

 is formed by the posterior inferior angle of the parietal and the superior border of 

 the mastoid portion of the temporal. 



The sutures at the base of the skull (Fig. 98) are the basilar in the centre, and on 

 each side the petro-occipital, the masto-occipital, the petrosphenoidal, and the 

 squamosphenoidal . 



The basilar suture (fissura sphenooccipitalis) is formed by the junction of the 

 basilar surface of the occipital bone with the posterior surface of the body of 

 the sphenoid. At an early period of life a thin plate of cartilage exists between 

 these bones, but in the adult they become fused into one (synchondrosis spheno- 

 occipitalis). Between the outer extremity of the basilar suture and the termina- 

 tion of the lambdoid an irregular suture exists, which is subdivided into two por- 

 tions. The inner portion, formed by the union of the petrous part of the temporal 

 with the occipital bone, is termed the petro-occipital fissure (fissura petrooccipitalis). 

 The outer portion, formed by the junction of the mastoid part of the temporal 

 with the occipital, is called the masto-occipital suture (suture occipitomastoided) . 

 Between the bones forming the petro-occipital suture a thin plate of cartilage exists; 

 in the masto-occipital is occasionally found the opening of the mastoid foramen. 

 Between the outer extremity of the basilar suture and the sphenoparietal an irregu- 

 lar suture may be seen, formed by the union of the sphenoid with the temporal 

 bone. The inner and smaller portion of this suture is termed the petrosphenoidal 

 fissure (fissura sphenopetrosa); it is formed between the petrous portion of the 

 temporal and the greater wing of the sphenoid; the outer portion, of greater 

 length and arched, is formed between the squamous portion of the temporal and 

 the greater wing of the sphenoid; it is called the squamosphenoidal suture (sutura 

 sphenosquamosa). 



The cranial bones are connected with those of the face, and the facial bones 

 with each other, by numerous sutures, which, though distinctly marked, have re- 

 ceived no special names. The only remaining suture deserving especial considera- 

 tion is the transverse suture. This extends across the upper part of the face, and 

 is formed by the junction of the frontal with 'the facial bones; it extends from the 

 external angular process of one side to the same point on the opposite side, and 

 connects the frontal with the malar, the sphenoid, the ethmoid, the lacrimal, the 

 maxillae, and the nasal bones on each side (sutura zygomaticofrontalis; the orbital 

 portion of the sutura sphenofrontalis, sutura frontoethmoidalis, sutura frontolacri- 

 malis, sutura frontomaxillaris, sutura nasofroutalis). 



The sutures remain separate for a considerable period after the complete for- 

 mation of the skull. It is probable that they serve the purpose of permitting the 

 growth of the bones at their margins, while their peculiar formation, together 

 with the interposition of the sutural ligament between the bones forming them, 

 prevents the dispersion of blows or jars received upon the skull. Humphry 

 remarks, "that, as a general rule, the sutures are first obliterated at the parts in 

 which the ossification of the skull was last completed viz., in the neighborhood 

 of the fontanelles; and the cranial bones seem in this respect to observe a similar 

 law to that which regulates the union of the epiphyses to the shafts of the long 

 bones." The same author remarks that the time of their disappearance is 

 extremely variable; they are sometimes found well marked in skulls edentulous 

 with age, while in others which have only just reached maturity they can hardly 



