32 



Bones of the Skull. 



Processus zygomaticus '.-> --W* 

 ossis frontalis ^ 



Processus fronto- 

 sphenoidalis 



Processus zygomaticus 

 ossis temporalis 



Processus temporalis 

 ossis zygomatici 



Processus frontosphenoidalis 



Foramen 



zygomatico- 



orbitale 



Facies 



orbitalis 



Probe in, 



foramen zygomatico- 

 temporale 



Facies malaris 



Os lacrimale 



Foramen 

 infraorbitale 

 Lamina papyracea 

 ossis ethmoidalis 

 Foramen zygomaticofaciale 



Surface which lies upon the 

 processus zygomaticus maxillae 



Facies temporalis 



Os xyg-omaticnm 



40 and 41. Right yoke bone, os zygomaticum. 



From without. From within. 



The os zygomaticum or yoke bone (0. T. malar bone) (see also Figs. 5560, 69 72), 

 is paired and lies in the lateral part of the facial skull. It has three surfaces. Tho laterally 

 directed fades malaris is quadrangular, fairly smooth, markedly convex and presents the 

 foramen zygomaticofaciale (0. T. malar foramen). The concave fades orbitalis, directed 

 median ward and forward, helps to form the lateral and inferior wall of the orbit and meets 

 the facies malaris, forming a markedly curved concave margin, which below completes the 

 margo infraorUlalis, and above forms the lateral margin of the aditus orbitae. The medial 

 inferior margin of the facies orbitalis unites with the lateral angle of the facies orbitalis cor- 

 poris maxillae (sutura zygomaticomaxillaris) and forms in half the cases the lateral boundary 

 of the fissura orbitalis inferior; the medial upper margin lies upon the margo zygomaticus of 

 the ala magna oss. sphenoidalis (sutura sphenozygomatica). On the facies orbitalis can be 

 seen the single or double foramen zygomaticoorbitale (Q. T. temporo-malar canals), the entrance 

 to a bifurcating canal (sometimes double from the beginning), the divisions of which perforate 

 the bone and end on the facies malaris and the facies temporalis (for the r. zygomaticofacialis 

 et r. zygomaticotemporalis n. zygomatici). The facies temporalis looks downward and median- 

 ward, is curved so as to be markedly concave and forms the anterior part of the fossa tem- 

 poralis. Here the foramen zygomaticotemporale is visible; medianward it adjoins a rough 

 surface for broad union with the proc. zygomaticus corporis maxillae (sutura zygomatico- 

 maxillaris). . 



At the upper angle of the facies malaris lies the processus frontosphenoidalis (0. T. 

 frontal process), in front for union with the proc. zygomaticus oss. frontalis (sutura zygo- 

 matico frontalis) , behind with the large wing of the sphenoid (vide supra). From the posterior 

 angle of the bone goes off the slim processus temporalis (0. T. zygomatic process), which 

 unites with the proc. zygomaticus oss. temporalis by a serrated suture (sutura zygomatico- 

 temporalis) to form the arcus zygomaticus. 



