2 THE SURGICAL ANATOMY OF THE HORSE 



the orbit (of which it forms part of the roof) to meet and articulate 

 with another osseous ridge which extends outwards from the extremity 

 of the occipital crest, and then downwards to meet the supra-orbital 

 process as stated. This process is the zygoma or the squamous temporal 

 bone. 



Near the root of the supra-orbital process palpation will reveal 

 the presence of a foramen, also called the supra-orbital, which should 

 be carefully located. 



Below the divergent ridges, which are the continuations inferiorly 

 of the sagittal crest, is a large area which narrows as we descend, 

 and which terminates inferiorly in a projection on the middle line 

 above the nostril. Throughout this area we find subcutaneous bone, 

 the frontal bones underlying the skin of the upper part, and the nasal 

 bones underlying the skin of the lower part, and the hard inferior 

 extremity is formed by the peak of the last-mentioned bone. This 

 area will be found to be resonant on percussion, for underneath it lie 

 the frontal sinuses and nasal fossae, and this is the region where the 

 operations of trephining into these chambers are performed. This 

 point should be carefully remembered in connection with the diagnosis 

 of empyema of the facial sinuses, when the resonance of the area 

 over the sinuses is absent on percussion. In its stead we have a dull 

 sound. 



Taking a lateral view of the head, in almost the centre of the 

 picture is placed the zygomatic ridge of the superior maxillary bone. 

 This ridge stands out prominently, and is easily seen in the living 

 subject ; it terminates abruptly at its inferior extremity, and is 

 continuous superiorly with a ridge on the malar bone, and this latter 

 again with the zygomatic process of the squamous temporal bone. 

 Superiorly placed to the ridge is the elongated elevation which 

 corresponds to the belly of the levator labii superioris proprius muscle 

 and the tendinous fibres of origin of the levator labii superioris alajque 

 nasi. The levator labii superioris proprius muscle should be carefully 



