180 sHOEiNa: 



This small bone, which in a horse sixteen hands high mea- 

 sures only two and a quarter inches in its longest diameter, 

 tliree-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 over- 

 laid 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, 

 the appearance is greatly changed, the furrows and roughness 

 giving place to a comparatively smooth surface. This change 

 is probably produced by the shoe limiting, if not destroying, the 

 expansive power of that part of the horn to which it is nailed : 

 whereby a change of structure in the membrane itself, as ^* ,ii as 



