268 ' Journal of Agriculture. [8 May, 1907. 



At birth and until the age of three or foiu- years the two splint bones 

 are attached to each other by the fibrous tissue C(.)nstituting the interosseous 

 ligaments; but at about four years, or earlier if the horse's work has in- 

 volved inordinate concussion, homologous union between the bones com- 

 mences. This may be signalized bv an obvious enlargement or outgrowth 

 of bone — yclept a splint — or by lameness, but it occurs in all horses and 

 is a progressive process, so that by the time the horse is "aged "" the 

 bonv union is complete throughout the whole length of the bones. A 

 visit to a knacker's yard would quickly satisfy any sceptic that the three 

 metacarpal bones in most horses over seven or eight vears are completelv 

 united. It would hence appear that the union between the large and small 

 metacarpal bones, by means of "splints,"' is merelv evidence that their 

 natural fusion into one solid bone, able to withstand the concussive strain 

 that modern horse-work involves, is gradually taking place under our very 

 eyes so to speak. The age period of splints is gradually lessening, for we 

 learn from writers on veterinary subjects in the earlv part of last century 

 that the age period in those days was from five to six years instead of 

 from three to- five, or even earlier, as it is now. There seems therefore 

 to be justification for the assumption that, if the experience of the last 

 hundred years is continued, it may not be many centuries before horses 

 will be born with the three metacarpal bones fused into one bone, as they 

 are now in later years. 



Causes. — The immediate cause exciting to splint formation is the 

 concussive strain put upon the fibrous connexion between the bones by the 

 incessant banging of the ground during action, whereby an inflammation of 

 this connecting tissue and of the fibrous covering of the bone {feriostenm) 

 is induced. Inflammations of this character involving the periosteum 

 always result, in horses, in a deposition of bonv matter in the swelling ; and, 

 according as the inflammation is severe or mild, the lameness, and the size 

 of the bony enlargement, will vary in degree. Splints mostly occur on 

 the inside of the cannon bone because the strain is greatest on the inner 

 splint bone, on account of it being more directlv under the centre of gravitv 

 and consequently having to sustain a greater weight-shock than the outer 

 bone. Similarly it is because the hind limbs are not called upon to Ijear 

 so much weight as the fore limbs that splints on the hind cannons are 

 rare. Another reason for the more frequent incidence of splints on the 

 inside is that the trapezoid bone of the knee rests wholly upon the head 

 of the inner splint bone and consequently the strain of concussive shock on 

 this bone has to be whollv borne bv the interosseous fibrous tissue uniting it 

 with the cannon bone ; whereas on the outside the corresponding knee bone 

 (the unciform) rests partlv on the head of the cannon bone as well as on 

 the splint bone, so that the weight-shcck, being borne by both bones, will 

 not cause such a severe strain on the interosseous tissue between the ex- 

 ternal splint and cannon bones. 



From what has been said it will be obvious that horses with high action 

 which V)Ang the ground heavily are prone to splints, as are also young 

 soft-boned horses when first used on hard roads or tracks. 



There are five Varieties of Splints described: — 



I. Simple Splint situated from li to 2 inches below the knee where 

 it does not interfere with the action of the knee-joint or the movement of 

 the flexor tendons or the suspensory ligament. In most cases onlv trifling 

 lameness, if anv, is caused by this class of splint and as it does not detract 



