126 



SKELETON OF THE OX 



the two plates of the bone come together. The cavity is very irregular and is sub- 

 divided into numerous spaces by ridges and partial septa. This multilocular 

 character is most marked in the anterior part, and here several small spaces appear 

 to he cut off from the main cavity (Baum). The supraorbital canal passes through 

 the sinus. Several small openings lead from the sinus to the ethmoidal meatuses, 

 and thus indirectly to the upper division of the middle meatus nasi. The communi- 

 cations with the cavity of the superior turljinal and with the lacrimal part of the 

 maxillary sinus which are seen in the macerated skull are closed in the fresh state 

 by mucous mem])rane. 



The maxillary sinus is excavated chiefly in the maxilla, lacrimal, and malar, 

 and is not divided by a septum as in the horse. It extends forward as far as the 

 facial tuberosity, or a little further in old animals. Its upper limit is indicated 

 approximately by a line drawn from the infraorbital foramen to the upper margin of 

 the orbit. It is continued directly backward into the lacrimal bulla to a point 

 nearly o]iposite to the ])ifurcation of the zygomatic process of the malar. It also 

 extends upward and backward through a large opening into a cavity formed by the 



Fig. 98. — Skull op Ox, Lateral View without Mandible. 

 The maxillary, lacrimal, and turbinal sinuses have been opened, and a portion of the orbit removed, a. 

 Cavity of superior turbinal bone; b, lacrimal sinus; c, maxillary sinus; d, communication between maxillary and 

 palatine sinuses; e, opening between maxillary and lacrimal sinuses; /, thin osseous bulla; g, lacrimal bulla; 

 h, orbit; 1—6, cheek teeth; 7, nasal bone; 8, premaxilla (nasal process); 9, maxilla; 9', infraorbital foramen; 

 10, frontal bone; 11, lacrimal bone; 1£, malar bone; 13, fissure between nasal bone and maxilla; 14, temporal 

 bone (squamous); 15, external auditory meatus; 16, styloid or paramastoid process; 17, occipital condyle; 

 IS, palate bone (peri)endicular part); 19, pterygoid bone (hamulus); 20, tympanic part of temporal; 20', mus- 

 cular process of petrous temporal. (After EUenberger, in Leisering's Atlas.) 



lacrimal, frontal, ethmoid, and turbinal bones, at the inner side of the orbit."^ 

 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 mueli 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 comnumication 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 

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

 posterior part of the sinus. 



' This is termed the hicrimal sinus liy some authors. It is similar in location and in the posi- 

 tion of its orifice to the turbinal part of the frontal sinus of the horse, with the important difference 

 that it does not communicate with the frontal sinuses in the ox. 



