VISCERAL ANATOMY. 



169 



The Keratogenous Membrane encloses the whole of the pre- 

 ceding structures, being itself enclosed by the hoof. 



It consists of the coronary cushion, velvety and laminal tissues. 



FIG. 27. 



LONGITUDINAL MEDIAN SECTION OF THE FOOT. 



[.Anterior extensor of the phalanges, or extensor pedis; 2, Lateral extensor, or ex- 

 tensor suffraginis; 3, Capsule of metacarpo-phalangeal articulation; 4, Large 

 metacarpal bone; 5, Superior flexor of the phalanges, or perforatus; 6, Deep 

 flexor, or perforans; 7, Sheath; 8, Bursa; 9, Sesamoid bone; 10, Ergot and fatty 

 cushion of fetlock; n. Crucial ligament; 12, Short sesamoid ligament; 13, First 

 phalanx; 14, Bursa; 15, Second phalanx; 16, Navicular bone; 17, Plantar cushion; 

 18, Third phalanx; 19, Plantar surface of hoof; 20, Sensitive or keratogenous 

 membrane of third phalanx. 



The Coronary Cushion resembles the derma, and forms the 

 upper border of the membrane. Its inferior boundary is a white 

 ring. Its superior has a margin, the perioplic ring. The extrem- 

 ities end behind in the velvety tissue. On its surface are numer- 

 ous papillae. 



The Velvety Tissue is also papillary in structure, covering the 

 plantar surface of the third phalanx and plantar cushion. At 



12 



