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. 



I, Anterior extensor of the phalanges, or extensor pedis; 2, Lateral extensor, or extensor suf- 

 fraginis; 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; 11, Crucial ligament; 

 12, Short sesamoid ligament; 13, First phalanx; 14, Bursa; 15, Second phalanx; 16, 

 Navicular bone; 17, Plantar cushion; t8, 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 



