LOWER JAW IN THE DOG. 173 



in other mammals, by which the cavity of the mouth is power- 

 fully contracted into a narrower space. 



Lower Jaw. The lower jaw-bone in the dog closely con- 

 forms to the common type of that bone in carnivorous mam- 

 mals. The general character of the jaw-bone has been already 

 described somewhat particularly under the horse (p. 23). As 

 in other mammals, the jaw-bone in the dog has the V shape, 

 with the upper extremities bent to an angle, and the part 

 directed upwards being known as the ramus. This ramus 

 divides at its upper extremity into the coronoid process, to 

 which the temporal muscle is attached, and the condyloid 

 process, which articulates with, the temporal bone. As in 

 carnivorous mammals in general, the ramus, or ascending 

 part of the jaw, in the dog, is much shorter, and particu- 

 larly the part which bears the condyle, than in the horse, ox, 

 and sheep ; the part of the ascending ramus which bears the 

 coronoid process is, however, well developed both in breadth 

 and height. This last process, indeed, in the dog, forms the 

 chief part of the ascending ramus. There is a deep fossa on 

 the external aspect, of which there is hardly a trace in the 

 vegetable-feeders, designed to lodge the muscle which descends 

 from the zygomatic arch to the jaw. The angle itself, by 

 which the ascending branch is joined with the body of the jaw, 

 is more open than in man and the vegetable-feeding mammals ; 

 so that the masseter muscle acts perpendicularly on the coro- 

 noid process, which occupies the anterior part of the ramus. 

 The angle itself posteriorly presents in the dog a considerable 

 projection, by which the extent of the attachment of the mas- 

 seter muscle is increased. 



The condyle, which is received into the squamous part of 

 the temporal bone, is prolonged transversely, and rounded ; 

 while the glenoid cavity into which it is received is deeply 

 hollowed out, and is guarded by a bony process before and 



