416 THE AiTATOMT OF VERTEBRATED ANIMALS. 



the motion of the jaw to the vertical plane. The supra- 

 orbital processes of the f rentals are small and pointed. The 

 root of the alisphenoid is traversed by a longitudinal canal. 

 The tympanum is boimded below by a convex osseous 

 wall, which is termed the iulla. It opens externally by the 

 short external meatus, at the inner end of which is a cir- 

 cular elevation for the attachment of the tympanic mem- 

 brane. A short distance internal to this frame for the 

 membrane of the di-um, a low crest rises from the floor 

 of the buUa and imperfectly divides it into an outer and 

 anterior portion which communicates with the Eustachian 

 tube, and an inner blind spheroidal cavity which occupies 

 the greater part of the bulla. The part of the bulla which 

 forms the floor of this cavity is the result of the ossification 

 of a process of the periotic cartilage, while the other part 

 is furnished by the tympanic bone. The low crest is 

 produced by the conjunction of both. Posteriorly and 

 internally, the periotic region of the buUa presents a canal, 

 through which the internal carotid artery passes. The 

 posterior opening of the carotid canal looks into the fora- 

 men lacerum posticum, and is not visible without dissection. 

 There is a large paroccipital process, with a prominent free 

 extremity; but, for the greater part of its length, it is closely 

 applied to the back of the buUa. The condyloid foramen 

 is quite distinct from the foramen lacerum posterius. A 

 large foramen behind the glenoidal cavity transmits a vein 

 from the interior of the skuU. In the nasal cavity, the 

 ethmoidal turbinals are very large ; the superior turbinals 

 are prolonged into the great frontal sinus, and the inferior 

 turbinals unite, in the middle line, with the septum. 



The clavicles of the Dog are always rudimentary and 

 are generally represented only by a gristly intersection of 

 the muscles which represent the sterno-mastoid and deltoid. 



The olecranar fossa of the humerus is perforated. The 

 hallux is much shorter than the other digits. When 

 the Dog stands, the metacarpal bones of these digits are 

 nearly vertical ; the basal phalanges are horizontal ; the 

 middle and the distal phalanges are inclined in the form of 



