BONES OF THE THORACIC LIMB 



145 



the bifurcation of the zygomatic process of the malar. It also extends upward and 

 backward through a large opening into a cavity formed by the lacrimal, frontal, 

 ethmoid, and turbinal bones, at the medial side of the orbit.i The floor of the cavity 

 Is irregular and the roots of the last three or four cheek teeth project up into it, 

 covered by a plate of bone. The sinus communicates with the palatine sinus freely 

 over the infraorbital canal through an oval opening about two to three inches (ca. 

 5 to 7.5 cm.) long. Above this it communicates by a shorter and much narrower 

 opening with the middle meatus nasi. 



The palatine sinus is excavated in the hard palate, and is separated from that 

 of the opposite side by a median septum. It extends from the posterior border of 

 the palate to a plane an inch or more (2.5 to 3 cm.) in front of the first cheek tooth. 

 As mentioned above, there is a large communication with the maxillary sinus over 

 the infraorbital canal, so that the cavity is sometimes regarded as a part of that sinus. 

 The large defect in the bony roof of the sinus is closed by two layers of mucous 



Fig. 143. — Skull of Ox; Lateral View without Maxdible. 

 The maxillary, lacrimal, and turbinate sinuses iiave been opened, and part of the orbital margin removed, a, Cavity 

 of dorsal turbinate bone; b, lacrimal sinus; c, maxillary sinus; d, communication between maxillary and palatine 

 sinuses; e, opening between maxillary and lacrimal sinuses; /, thin osseous bulla; 3, lacrimal bulla; h, orbit; 1-6, cheek 

 teeth; 7, nasal bone; 8, premaxilla (nasal process); 9, maxilla; 9', infraorbital foramen: 10, frontal bone; 11, lacri- 

 mal bone; IJ, malar bone; 13, fissure between nasal bone and maxilla; i4, temporal bone (squamous) ; i5, external 

 acoustic meatus; i^, paramastoid process; i 7, occipital condyle; ^5, palate bone (perpendicular part); ?5, pterygoid 

 bone (hamulus); ^0, tympanic part of temporal; jSO', muscular process of petrous temporal. (After Ellenberger, in 

 Leisering's Atlas.) 



membrane in the fresh state. The palatine canal passes obliquely through the 

 posterior part of the sinus. 



The sphenoidal sinus is almost entirely in the sphenoid bone and does not 

 communicate with the palatine sinus. It has one or two openings into the ventral 

 ethmoidal meatuses. There is no cavity in the perpendicular part of the palate 

 bone. 



There are several small air-cavities between the lateral mass of the ethmoid 

 and the anterior part of the frontal sinus, which communicate separately with 

 ethmoidal meatuses. 



BONES OF THE THORACIC LIMB 



The scapula is more regularly triangular than in the horse, relatively wider at 



the vertebral end and narrower at the distal end. The scapular index is about 



1 : 0.6. The spine is more prominent and is placed further forward, so that the 



supraspinous fossa is narrow and does not extend to the lower part of the bone. 



1 This is termed the lacrimal sinus by some authors. It is similar in location and in the posi- 

 tion of its orifice to the turbinate part of the frontal sinus of the horse with the miportant ditter- 

 ence that it does not communicate with the frontal sinus in the ox. 

 10 



