284: OUTLINES OF EQUINE ANATOMY. 



■wliicli tlius intervenes between the coronary secreting sub- 

 stance and the bone at this part. This surface is perforated 

 by numerous foramina, and presents small irregular plates 

 running from above, most marked near the inferior mar- 

 gin, where, also, at varying distances from each other, are 

 large foramina for the passage of the anterior branches of 

 the interosseous plantar artery, which assist to form the 

 circumflex artery of the toe. Supero-laterally is a deep 

 depression, smooth at its bottom for attachment of the 

 lateral ligament of the coffin-joint. Behind this is the 

 alct, running backwards for attachment of the lateral car- 

 tilage, which also seems to continue the bone from the pos- 

 terior margin of this surface, assisting to form a foramen 

 through which the lateral laminal branch of the plantar 

 artery runs, coursing its way through a groove in a forward 

 direction between the bone and the sensitive laminse ; at 

 the anterior extremity of the bone it enters its substance 

 through a large foramen. It sends off numerous branches, 

 especially one running straight downwards, for which 

 there is a special secondary groove, and which forms the 

 commencement of the circumflex artery of the toe. The 

 posterior margin of this surface presents superiorly the 

 ala, inferiorly the angles of the plantar surface ; between 

 these two is the lateral laminal groove. They are rough, 

 and are directly continuous with the lateral cartilage. In 

 consequence of its porous nature, and the close reticula- 

 tion of blood-vessels in its substance, os pedis seems to be 

 soft, but its structure in the dried bone will be found to 

 be remarkably hard. 



Attached to the upper margin of the alae of os pedis, 

 extending superiorly for about one and a half inches, 

 posteriorly for about one and a half inches behind the 

 posterior extremities of the alse, and extending farthest 

 forward at the superior part of their anterior margin, 

 are the lateral cartilag^es of the foot. These are pecu- 

 liar shaped portions of cartilage which present two sur- 

 faces, three margins. The external surface is convex, 

 extending at first upwards from the wing of os pedis with 

 an outward inclination, which is increased along its pos- 

 terior margin. Its anterior extremity becomes ultimately 

 blended with the dense fibrous tissue which, in this situa- 

 tion, seems to closely unite the lateral ligament of the 

 pedal-joint with the extensor pedis tendon at its inferior 



