224 HOW TO SHOE A HORSE. 



the healthy condition of this bone, and the joint formed 

 between it and the tendon, which passes under it to the 

 coffin bone, and is called the navicular joint, mainly de- 

 pends the usefulness of the horse to man. 



This small bone, which in a horse sixteen hands high 

 measures only two and a quarter inches in its longer di- 

 ameter, three-fourths of an inch at the widest part of its 

 shorter diameter, and half an inch in thickness in the 

 centre, its thickest part, has the upper and under surfaces 

 and part of one of the sides overlaid with a thin coating 

 of gristle, and covered by a delicate secreting membrane, 

 very liable upon the slightest injury to become inflamed ; 

 it is so placed in the foot as to be continually exposed to 

 danger ; being situated across the hoof, behind the coffin 

 bone, and immediately under the coronet bone ; whereby 

 it is compelled to receive nearly the whole weight of the 

 horse each time that the opposite foot is raised from the 

 ground. 



The coffin bone consists of a body and wings ; and is 

 fitted into the hoof, which it closely resembles in form. Its 

 texture is particularly light and spongy, arising from the 

 quantity of canals or tubes that traverse its substance in 

 every direction, affording to numerous blood-vessels and 

 nerves a safe passage to the sensitive and vascular parts 

 surrounding it ; while the unyielding nature of the bone 

 effectually protects them from compression or injury, under 

 every variety of movement of the horse. 



In an unshod foot, the front and sides of the coffin bone 

 are deeply furrowed and roughened, to secure the firmer 

 attachment of the vascular membranous structure, by which 

 the bone is clothed ; but in the bone of a foot that has 

 been frequently shod, this appearance is greatly changed, 

 the furrows and roughness giving place to a comparatively 

 smooth surface. This change I imagine to be produced 



