1895.] on the Structure and Function of the Horse 's Foot. 557 



we shall have to deal with more fully later on, is permitted to occur 

 through the young moist born which exists at this part. 



From the heel the weight is transmitted along the foot from rear 

 to front, and finally the heel becomes raised, the toe alone bearing on 

 the ground. This is the position in which the greatest wear and tear 

 of the foot occurs, for the toe is now engaged in piving the propulsion 

 to the body, the friction is therefore considerable, and to meet this 

 the horn at this part is comparatively dry and very tough. 



We can see, therefore, that the variations in the amount of moisture 

 in the wall are intended to meet the wear and tear of the foot. 



The use of the wall is to support the weight of the body : the 

 horse's weight is literally slung inside its foot. This slinging appa- 

 ratus is infinitely stronger than if the weight were imposed, as we 

 might imagine, on the sole of the foot, and, in addition, it is dis- 

 tributed over a larger surface than it otherwise would be. 



When we remember that the mean weight of a horse is 10 cwt., 

 and there are many which weigh 15 cwt. or more, there is no 

 difficulty in observing that the foot is really an extremely small base 

 on which to impose this enormous weight. The area of the human 

 foot aj>pears to be greater than that afforded by the horse's foot, but I 

 shall now have to show you that the slinging apparatus previously 

 spoken of, increases in a remarkable manner the internal surface of 

 the horse's foot without adding to its circumference. 



Found on the inside of the wall are 500 or 600 plates or leaves 

 of horn, which run in the direction of the fibres of the foot — they may 

 be seen in this model. In length they nearly correspond to the wall, 

 whilst they are so thin as to be perfectly transparent. Regarded by 

 themselves their function is not very evident ; but if we examine the 

 exterior of the sensitive foot, it will be observed that it is covered 

 with a very large number of delicate sensitive leaves, also of extreme 

 thinness, and so fall of blood-vessels as to give a bright red colour to 

 the part. 



These sensitive leaves or lamina) correspond in number and 

 position to their insensitive counterpart, and the two sets are 

 found to be fitted into each other in such a way as to form the most 

 perfect dovetail. 



This dovetailing of the laminae produces immense strength : by no 

 ordinary process is it possible to destroy the union of these two 

 surfaces, even after death ; special methods have to be adopted in the 

 study of anatomy if we wish to separate the horny from the sensitive 

 laminae. 



But the dovetailing is further increased in strength by a remark- 

 able arrangement. If we make a horizontal section of the two sets of 

 lamina? in position, and examine them microscopically,* we find that 



* A number of microscopical preparations were placed on the library table 

 illustrating the structure of the foot. The majority were kindly prepared for 

 this lecture by Professor Mettam, B.Sc. Dick Veterinary College, Edinburgh. 



