ANATOMICAL STEUCTUKE OF THE SHEEP. 101 



portion in its posterior part has a shallow cavity for the articula- 

 tion of the lower jaw-bone. This cavity is shallow in herbivorous 

 animals, such as sheep, when compared with that in meat eating, 

 or carnivorous animals. This is due to the different modes 

 of mastication of the two classes, that of herbivora being a 

 grinding lateral motion, only a shallow articulation is required, 

 while in carnivora, which require to tear and rend their food 

 necessitating opening the jaws very wide, the articulation 1* 

 necessarily deep. 



The petrous portion of the bone is hard, flinty, apparently 

 a solid convex figure. It is the receptacle, however, for the 

 organ of hearing, and contains on it's internal face orifices for the 

 passage of the auditory nerve, with a corresponding larger one 

 on its external face for the passage of sound. 



The inferior and middle parts of the cranium are formed 

 principally by the sphenoid bone. This supports the middle 

 lobes of the cerebrum, and has many holes in it for the passage 

 of nerves and blood vessels. 



Anterior to and inferior to the cranial cavity we find an- 

 other called the nasal, which is separated from the cranial by a 

 hone called the ethmoid. This bone supports the anterior lobes 

 of the cerebrum, and has passages through it for the exit of the 

 olfactory nerves, which are those conveying the sense of smell 

 to the brain. This is the bone which is punctured when oper- 

 ating on "sturdy" or "giddy sheep," by passing a wire up the 

 nasal cavity through the ethmoid and puncturing the sack con- 

 taining the parasite in the cerebral part of the brain substance. 



The other bones of the head are those composing the part 

 called the face, viz., the frontal, nasal, superior maxillary, 

 lachrymal, anterior maxillary, palate bones, malar, and inferior 

 maxillary. These bones are of various sizes and shapes, in- 

 timately joined together, becoming blended almost into one 

 solid inass as the animal progresses in age. 



