184 BOARD OF AGRICULTURE. 



The word navicular means boat-like. That little boat shaped body 

 lies on the bottom of the coronet bone here and serves as a pulley 

 for the tendon to pass over into the bottom of the foot ; this pulley 

 process keeps the tendon off from the joint, a splendid provision of 

 nature. Otherwise it would interfere with the joint, and the tendon 

 would wear out in a short time. The navicular trouble, therefore, is 

 one of the ugliest types of disease, one of the most mysterious that 

 we have to contend with, one that is almost sure to be overlooked 

 by the ordinary farrier ; in fact, it is a lameness that is exceedingly 

 difficult to explain ; but if you will listen for a moment I will give 

 you the key so that you can diagnose this form of disease. In talk- 

 ing about an}' other part of the body the word joint means a union 

 of two bones ; but the "navicular-joint," so called, is a union of the 

 inside of the tendon with the outside of this little bone, that is 

 covered on the outer and under surface with a smooth, glistening 

 membrane. There is a little capsule and synovia, or joint-oil, is se- 

 creted. A horse often gets badly strained here, intlammation sets 

 in and interferes with the synovial secretion and the pla}- of this 

 peculiar joint. When a horse stands with his leg vertical and rests 

 on the heel the cord is put to the stretch. If he raises his heel the 

 cord is relaxed. If he stands with the foot pointing out in front 

 the cord is relaxed, and in that way the horse gets relief. A horse 

 with the navicular disease, therefore, is a ''pointer." There is 

 usually no malformation of the foot, but after some years' standing 

 you will see the heel becoming contracted, the foot will not be so 

 large, it will not be nourished as well, it will not be used as much, 

 the horse will do most of his work with the other foot. As soon as 

 he stops he raises the heel, and after standing a moment he puts the 

 foot out forward. When you see a horse with this disease standing 

 at a post you will see him shift from one of these positions to the 

 other. Such a lame horse will nod every time he steps on the well 

 foot. You might think he would bow when he steps on the diseased 

 foot, but it is not so ; he throws his whole weight on the well foot 

 and thus steps gingerly on the other, which is so characteristic of the 

 trouble in question. 



Question. What causes this navicular disease? 



Dr. Cresset. A strain ; stepping on a rolling stone ma}' start it, 

 b}' producing an injury to the cord, setting up a little inflammation. Of 

 the hundreds of such injuries, some result in this disease and others 

 recover without serious trouble. 



