144 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 be cut off from the main cavity. 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 dorsal turbinate and with the lacrimal part of the 
Fig. 142.—Sku.. or Ox; Dorsat VIEw. 
a, Frontal sinus; a’, cranial plate of frontal bone; 
The outer plate of bone has been removed to show the sinuses. 
a”, anterior part of frontal sinus, which is separated from remainder by a septum (b); c, c’, communications between 
frontal sinus and nasal cavity; d, supraorbital foramen; e, supraorbital canal; /, cavity of dorsal turbinate bone, 
and g,its opening into the nasal cavity; A, lacrimal sinus; 7, its communication with the maxillary sinus; /, maxillary 
sinus; J, orbit; 7, frontal bone; 1’, processus cornus; 2, nasal bone; 3, premaxilla (nasal process); 4, maxilla; 4, lacri- 
(After Ellenberger, in Leisering’s 
mal bone; 6, malar bone; 7, dotted line indicating course of nasolacrimal duct. 
Atlas.) 
maxillary sinus which are seen in the macerated skull are closed in the fresh state 
by mucous membrane. 
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 dorsal limit is indicated 
approximately by a line drawn from the infraorbital foramen to the upper margin 
of the orbit. It is continued into the lacrimal bulla to a point nearly opposite to 
