THE FOOT OF THE HORSE. 41 



der swells forward in a half-circle and obliquely up'ward to a 

 pyramidal eminence in its middle, on the front face of which is 

 inserted the attachments of the principal extensor tendon of the 

 foot, as shown in Fig. 4 and colored plates. 



The under face is hollowed out like an arch, corresponding 

 to the sole of the hoof, and here the terminal tendon of the deep 

 flexor of the foot — the flexor perforans — is inserted into the 

 semi-lunar crest, widening in a remarkable manner over the 

 median imprints, as shown in Fig. 12. 



There are two lateral wings to this bone directed back- 

 ward, on the summit of w^hich the lateral cartilages of the foot 

 are implanted. 



Bones and their Articulations. — In all those situations 

 which have to sustain violent eflbrts, the substance of the bones 

 is found to be very compact, formed of a proper tissue, covered 

 outside with a tough, elastic membrane — the periosteum — and 

 are abundantly supplied with blood-vessels and nerves for their 

 nutritive movement. On their articular surfaces — between the 

 opposing heads or facets combining in the joints — they are cov- 

 ered with layers of elastic cartilage, which are of the greatest 

 importance in the smooth gliding movements of the bones and 

 in the reduction of shocks and articular friction. AVhen they 

 are worn or transformed into bone, in consequence of cer- 

 tain articular maladies, the movements become painful and very 

 difficult. 



Ligaments and Lubricants. — The structures whose ofiice 

 is to brace and maintain the joints in contact and unite the 

 movable surfaces are the ligaments. These are powerful auxil- 

 iaries of the muscular forces, give permanent equilibrium to 

 the weight, and secure the firm and effective working of the 

 articular surfaces. A serous membrane covers the internal 

 face of the ligaments, which secretes the synovia, a kind of 



