LAMENESS IN THE FORE LEG 119 



clients in order to convince tlicni that a spherodial exostosis of 

 the proximal phalanx, in certain cases, is in reality ' ' ringbone, ' ' 

 even though there exists no exostosis which completely encircles 

 the affected bone. 



Etiolog'y and Occurrence. — Exostosis of the first and second 

 phalanges is usually due to some form of injury, whether it be a 

 contusion, a lacerated wound which damages the periosteum, or 

 periostititis and osteitis incited by concussions of locomotion, 

 or ligamentous strain. Practically the only exception is in the 

 rachitic form of ringbone which affects young animals. 



There are predisposing causes that merit consideration, chief 

 among which is the normal conformation of the coronet joint. 

 This proclivity is constant ; the normal interphalangeal articula- 

 tion is an incomplete ginglymoid joint and while its dorso-volar 

 diameter is great, this in no wise compensates for its dispropor- 

 tionately narrow transverse diameter. The pivotal strain which 

 is sometimes thro^Ml upon this articulation when an animal turns 

 on one foot, as well as the tension which is put on the collateral 

 ligaments when the inner or the outer quarter of the foot rests 

 in a depression of the road surface, tends to detach the insertion 

 of these ligaments or to cause fibrillary fractures of their sub- 

 stance. 



Short, upright, pasterns receive greater concussion during fast 

 travel on hard roads than do the longer more sloping and well 

 formed extremities. Those who are advocates of the theory that 

 this type of osteitis with its complications has its origin in the 

 articular portion of the joint, claim that the upright pastern con- 

 stitutes an important tendency toward ringbone. Howbeit, ring- 

 bone is an active, serious and frequent cause of lameness and it 

 affects animals of all ages and occurs under various conditions. 

 Horses having good conformation and kept at work wherein no 

 great amount of strain is put upon these parts, are occasionally 

 victims of this affection. 



Classification. — The arrangement employed by Moller^ is in- 

 tensely practical and logical. He considers ringbone as articu- 

 lar, periarticular, rachitic and traumatic. A mode of classifica- 



iRegional Veterinary Sui-gery MiiUer — Dollar, page G05. 



