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and is secreted by the tissue covering the coffin bone ; it is 

 soft, thick, and light of color. These different kinds of horn, 

 in a healthy foot, interlace with each other as they grow, and 

 unite to form one solid substance. The union of these 

 secretions forms a thick, elastic and strong body, to which 

 an iron shoe can be safely nailed, and whereon the enormous 

 bulk of the horse's frame may with safety rest. 



We have already said that there is attached to the wings 

 of the coffin bone the lateral cartilages; these give form, 

 substance, and elasticity to the heels upwards. This widely 

 distributed tissue passes downwards and fills up all the 

 sinuosities, and takes strong attachments to the processes 

 of the coffin bone. These lateral cartilages then pass hori- 

 zontally inwards, passing over the horny sole and bars, and 

 intimately unites with the sensitive frog or plantar cushion. 

 This sensitive frog fits admirably into the horny frog, and 

 forms a pad or cushion. 



The immediate purpose of these cartileges are : ist. The 

 interposition of this elastic tissue between the hard hoof 

 and the hard bone, and prevent shock and concussion as 

 the foot strikes the ground; 2d, It equalizes the pressure of 

 the bones of the foot on the broader surface of the hoof; 

 3d, It allows more play and motion to the heels at every 

 step. 



We thus perceive that within the horny box or hoof there 

 are very different kinds of tissue, namely, fascia, cartilage, 

 cellular, and fibro-cellular tissue, vessels and nerves, be- 

 sides the coffin and navicular bones. Without some under- 

 standing of the structure and function of these sensitive tis- 

 sues it is impossible to understand the seat and nature of 

 the diseases to which the foot is subject, nor their successful 

 treatment. As examples of the diseases to which these tis- 

 sues are subject we may state here that when the coronary 

 substance is divided by a sharp instrument or any accident, 

 we have a division in the wall of the hoof to a certain depth ; 

 when it is lacerated or part of it torn away, false quarter is 



