676 A MANUAL OF VETERINARY PHYSIOLOGY 



lateral cartilage explains the cause of lameness in ' side-bone ' — 

 viz., the squeezing of the sensitive structures between the wall 

 on the one hand and the ossifying cartilage on the other. 



The folding up of the horny and vascular leaves in the foot, 

 in the manner previously described, has another function besides 

 that of merely supporting the weight and rendering the union 

 firm. Reference has previously been made to the remarkably 

 small size of the horse's foot in proportion to the size of his body. 

 Comparing the horse's foot, so far as size is concerned, with the 

 human foot, the advantage in the majority of cases lies on the 

 side of the biped. The most interesting fact which physiology 

 has to demonstrate is that, though the foot presents a small 

 circumference, in reality it encloses a vast area, due to the 

 anatomical arrangement of the laminae. It is clear that by the 

 process of folding up material within, the surface of the foot is 

 considerably increased. In other words, by this arrangement 

 the foot has been kept within small proportions without affecting 

 its strength. A book, say of 600 pages, may, by placing one 

 leaf on the other, be made to occupy a bulk represented by a 

 few inches ; but if each page be laid out separately on the ground, 

 and made to touch the others, the surface covered will be con- 

 siderable. This is exactly what occurs in the foot ; the insensitive 

 and sensitive leaves by their singular arrangement increase the 

 surface of the foot, and yet keep it within reasonable limits. 

 Bracy Clark, one hundred years ago, was the first to recognise 

 this provision, and had a calculation made as to the increased 

 surface afforded, which was considered to be equal to ij square 

 feet. Moeller* has estimated that it is equivalent to 8 square 

 feet, whilst Gader's estimate f is iof square feet. For safety 

 Moeller's number is adopted. The bearing surface afforded by 

 each foot is equivalent to 8 square feet, giving a total area of 

 32 square feet. It is evident, that as feet vary greatly in size; 

 this surface must accordingly be greater or less. 



The physiological function of the leaves of the foot is demon- 

 strated by pathological observation. Inflammation of the 

 laminae, apart from septic or intestinal poisons, occurs either 

 through severe work or through an animal standing too long 

 in one position ; in either case the parts get strained. The prac- 

 tical value of exercising horses which from any cause have to 

 stand for a length of time is well known ; exercise overcomes the 

 tendency of the laminae to congestion from continual strain, and 

 the feet not only become cool, but the animal may continue 

 standing for a considerable time if exercised daily. The treat- 

 ment of laminitis by exercise possesses a sound physiological 



■ * Op. cit. 

 ■]• Goubaux and Barrier, ' Exterior of the Horse ' (translation) . 



