130 PHYSIOLOGY OF FARM ANIMALS [CH. 



of the hoof is an essential qualitj^, as without it the structure 

 would no longer act as an anti-concussion mechanism. 



The actual horny material is a protein of the following 

 approximate composition : 



Salts (chlorides, sulphates, and phosphates of sodium, magnesium, 

 iron and silicon) are present in small amounts. The quantity 

 of water is variable. The foot-pad contains the most and the 

 wall the least. 



The laminae of the hoof are attached at the antero -lateral 

 part to bone, at the remaining parts to cartilage. The lateral 

 cartilages supply a movable attachment to the sensitive laminae, 

 and admit of their passing outwards. The lameness resulting 

 from side-bone (or ossification of the lateral cartilages) is due to 

 the sensitive structures within being squeezed between the 

 pastern bone and the ossified cartilage. 



The laminae of the hoof are much folded, and their entire 

 surface if spread out has been estimated at from 8 to 10| feet. 



Inflammation of the laminae occurs as a result of various 

 causes. It may be due to overwork, or it may be due to a horse 

 standing too long in one position when the laminae tend to 

 become congested. Such a tendency may be overcome by 

 exercise which relieves the congestion by causing the blood to 

 circulate. This is one of the recognised modes of treatment for 

 laminitis or founder. This disease frequently results in sej^ara- 

 tion of the horny and sensitive laminae, and may be followed 

 by descent of the coffin bone. 



The chief anti-concussion mechanisms may now be sum- 

 marised as follows: (1) the 3'ielding articulation of the coffin 

 bone, (2) the increase in the width of the foot when the heels 

 come to the ground (the process being one of expansion), (3) the 

 elastic foot-pad or frog, and (4) the slight up-and-down play 

 between the pedal bone and the sublaminal tissue as the weight 

 is removed from or comes on the foot. This latter movement is 

 participated in also by the horny sole. 



