768 



THE SENSE ORGANS AND SKIN OF THE HORSE 



sides, where it unites with the angles of the walls; the junction here is covered by 

 the expanded periople and constitutes the bulb of the hoof. 



Fig. 577. — Hoof of Horse, Right Fore Foot, 

 Ground Surface. 

 37, Inner quarter; 38, outer (luarter; 39, 

 ground border of wall (toe); 40, white line; 41, 

 sole; 4^, apex of frog; 4'^, lateral ridge of frog; 

 44, central furrow of frog; 45, lateral furrow be- 

 tween frog and bar; 4^5, bar. (After EUenberger- 

 Baum, Anat. fiir Kiinstler.) 



Fig. 578. — Horizontal Section of Hoof op Horse. 

 The section is cut just above the ridges of the frog 

 and bars and parallel with the ground surface. 1, Wall; 

 2, sole; 3, median ridge of frog; 4, lateral ridge formed 

 by junction of frog and bar; 6, median furrow over apex 

 of frog; 6, laminae of wall; 7 , lamina; of bar. 



The apex occupies the central angle of the concave border of the sole, and 



forms a blunt, round prominence a 

 little in front of the middle of the 

 ground surface of the hoof. 



Structure of the Hoof. — The 

 hoof is composed of epithelial 

 cells which are more or less com- 

 pletely keratinized except in its 

 deepest part, the stratum ger- 

 minativum; here the cells have 

 not undergone cornification, and 

 by their proliferation maintain the 

 growth of the hoof. The cells are 

 in part arranged to form tubes 

 which are united by intertubular 

 epithelium, and inclose medullary 

 cells and air-spaces. 



The wall may be regarded as 

 consisting of three layers. The 

 external layer consists of the peri- 

 ople and the stratum vitreum. 

 The periople is composed of soft, non-pigmented tubular horn. It is con- 

 tinuous with the epidermis above, and extends downward a variable distance. 



Fiu. 579. — Frontal Sf.ction op Hoof of Horse, Posterior 

 Part Vikwk» from i.\ Front. 

 /, Wall; Z, sole; 3, bar; 4, frog; 5, median ridge of 

 frog; 6, lateral ridge formed by junction of frog and bar; 7, 

 lamintD of bar; 8, laininu- of wall; 9, coronary groove; 10, 

 periople of heel. 



