THE HORNY LAMINA. 29 



There is now before me the coffin bone of a cart- 

 horse. It measures nine and a half inches round the 

 edge, four and a quarter inches across, from wing to 

 wing, and only just exceeds four ounces in weight. 



A similar principle is carried out in the hoof, 

 but, as the material is horn and not bone, it must be 

 treated in a different manner. 



In the hoof there are three distinct kinds of horn. 

 Each kind is secreted from a different source, and 

 is perpetually renewed when it becomes worn out or 

 effete. The three horns are, firstly, the outer ' crust ' 

 or ' wall ; ' secondly, the ' frog,' which occupies the 

 centre of the under surface of the hoof, and ought to 

 bear the weight of the horse when it first sets foot 

 to the ground ; and, thirdly, the ' sole,' which con- 

 nects the frosr with the wall. 



We will take each of these structures separately. 



Even the wall is not a solid piece of horn, but 

 is made of a great number of very thin horny plates 

 called ' laminae. ' These laminas are shaped like knife- 

 blades, the backs being very much thicker than the 

 edges. If we can imagine some six or seven hundred 

 of these horny blades to be set closely side by side, 

 their backs to be fused together and their edges free, 

 we may form some conception of this portion of the 

 hoof. They have been well compared to the gills 

 of a mushroom. 



