786 DISEASES AND THEIE TREATMENT. 



out of twenty-four, and sometimes for several consecutive days. 

 Let this be compared with the few hours during which the feet of 

 a horse at pasture are in a quiescent state, and there will be no 

 cause of surprise in the change of form and position, and character, 

 and the state of contraction which takes place in the foot deprived 

 of its natural pressure and motion. 



" The first indication of contraction is the gradual displacement 

 of the navicular and coffin-bones. They ascend" within the hoof. An 

 unnatural arch is formed by the ascent of the frog, and the delicate 

 synovial membrane lining the joint is crushed and bruised by the 

 very material which nature has bestowed as a defense. This bruise 

 of the synovial membrane lining the joint is the veritable source of 

 the complaint, the actual cause of the whole not consisting in the 

 wear and tear of the part, but having its origin in rest. It is en- 

 gendered in the stable, but it becomes permanently established by 

 sudden violence out of it. General contraction of the foot of the 

 horse may take place to a great extent with comparative impunity; 

 but it is a partial contraction or pressure which is the root of evil." 



Prof. Williams, our best modern authority, in relation to the 

 cause, says: 



" I have stated my opinion that generally the alteration of the di- 

 rection of the bony column by the shoe, or by a natural upright con- 

 formation of pastern, is the great cause. In addition to this violent 

 interference with the designs of nature, the elevation of the heels fur- 

 nishes additional cause of concussion to those already stated, by 

 removing the frog from the ground; the frog being elastic, tough, 

 and strong, intended to touch the ground and diffuse concussion, 

 as well as to prevent slipping at each step the animal takes. When 

 left in its natural condition, it is a large, tough, softish body, giv- 

 ing way to the pressure of the fingers when manipulated, expand- 

 ing each time the foot is put to the ground, the commissures at its 

 sides admitting of this expansion without the other parts of the foot 

 being interfered with. So long as it touches the ground, the sen- 

 sitive parts within, and particularly the navicular bursa, for which 

 it furnishes a soft bed, rests upon a resilient body, free from con- 

 cussive danger. Besides furnishing this soft bed, it performs 

 another important function, being elastic within and without, it 

 assists the flexors in the first act of elevating the foot from the 

 ground, and it does this in virtue of its inherent power of assuming 

 its original shape when the superincumbent weight is taken away 

 from it. Thus, whilst on the ground, and bearing its proportion of 

 weight, it is flattened from side to side, bulging into the commis- 

 sures and cleft, ready at every movement, like a piece of india- 

 rubber, to assume its proper form when the least portion of the 

 weight is taken from it. When the flexors are acting, it becomes 

 narrowed from side to side, and deeper from surface to surface, and 

 during this assumption of its natural form, it gives an upward im- 

 petus to the foot, which is of essential importance to its easy eleva- 

 tion. The removal of this frog pressure during long periods of rest 



