30 



are endowed with vitality, are nourished, grow, waste, and are 

 repaired, and undergo various mutations according to the age 

 of the animal, and they are subject to diseases analagous to 

 the soft parts." — Dadd. 



PARTICULAR DESCRIPTION OF THE BONES OF THE FOOT. 



Enumerating the bones of the foot in the order of size, the 



number either wholly or partially within the foot are three, 



namely : 



i. The Os Pedis. 



2. The Os Corona. 



3. The Os Naviculare. 



These three bones enter into the formation of the foot-joint. 



1. The Os Pedis, Foot or Coffin-Bone. 



The os pedis or coffin-bone belongs to the class of irregular 

 bones ; it possessing such a remarkable complexity of form. 

 Viewing it in front, its superior outline presents an eminence 

 somewhat like a pyramid in shape, and is therefore called the 

 pyramidal process. This process receives the insertion of the 

 tendon of the Extensor Pedis muscle by which the foot is ex- 

 tended during action. Immediately beneath the articular sur- 

 face that corresponds to that of the navicular bone, the tendon 

 of the flexor pedis perforans is inserted. The office of this 

 muscle, as its name implies, is to flex the foot. 



The whole of the anterior surface is very rough, which makes 

 the attachment of its periosteal membrane the more firmly ad- 

 herent. Large grooves for the protection of the larger blood- 

 vessels, the nerves and the absorbents, as well as holes for their 

 passage into the interior of the bone may be seen upon its 

 lateral surfaces. Its posterior aspect exhibits two surfaces for 

 articulating with the coronal and navicular bones. 



The prolongations of the bone backward on either side are 

 called the alae or wings of this bone. 



The inferior, or plantar surface, is comparatively smooth and 

 concave, and its general outline corresponds with that of the 



