368 The Farmer's Veterinary Adviser. 



the horny laminae and the hoof-wall, causing a falling in 

 of the wall anteriorly, and a descent of the margin of tho 

 coffin-bone so that it will press upon and even perforate 

 the sole (pumice foot). In other cases there is merely a 

 circumscribed horny growth pressing inward on the quick 

 at a particular point {Iceraphyllocele). If the secreting sur- 

 face of the sole is involved similar horny tumors may be 

 formed, as in corns. Disease of the secreting membrane 

 of the frog may determine an unhealthy secretion from the 

 cleft (thrush) or an excessive growth and loss of cohesion 

 of the horny fibres (canker). 



In addition to these disorders originating in the deeper 

 structures we have a further list that take their origin in 

 unnatural states of the horn. And for these the current 

 modes of shoeing are mainly chargeable. 



At all points the hoof undergoes a steady condensation 

 from its inner to its outer layers. In a transverse section 

 of the hoof-waU the deeper tubes are open, spacious and 

 surrounded by soft, yielding, elastic horn, while those 

 near the surface are exceedingly miaute and surrounded 

 by a far greater amount of dense, hard and exceedingly 

 resistant homy matter. The outer surface is especially 

 close in its texture, and as the tubes run through the 

 whole length of the wall to its lower or wearing surface, 

 where they are closed by attrition, comparatively little ex- 

 halation of moisture can take place from this part of the 

 horn in its healthy state. But it is far different when the 

 dense surface layer has been removed by the rasp, and 

 the open ends of the tubes exposed all over the sur- 

 face of the waU. Then evaporation and drying go on 

 rapidly, the hoof becomes hard and brittle and follows its 

 constant tendency, when dry, to turn in at the heels and 

 coronet, causing absorption of the parts beneath and lay- 

 ing the foundation of disease. 



The sole and frog naturally increase in density from 

 the quick outward, but the horn breaks up into plates be- 

 fore becoming detached, the plates being separated from 



