THE HOOF 



767 



referred to as forming the white Hne on the ground surface of the hoof. The angle 

 of junction is rounded internally and presents a number of low ridges and specially 

 large openings for the pajiilUe of the matrix. There is fre<iuently a ridge of larger 

 size at the toe. 



The concave border has the form of a deep angle which is occupied by the bars 

 and frog. By its junction with these it forms two pronounced ridges in the interior 

 of the foot. The parts of the sole between the wall and bars may be termed its 

 angles. 



3. The frog (Furca unguis) is a wedge-shaped mass which occupies the angle 

 between the bars and sole, and extends considerably below these on the ground 

 surface of the foot. It may be described as having four surfaces, a l^ase, and an 

 apex. 



Pcrioplc ut coromirij margin 



iinry groove 



Median furrow 



Lakral ridge 

 '^pine or frog-stay 



Fig. 576. — Ixternai. Surfatk of Part of Hoof of Horse. (After Schmaltz, XWa.^ d. .\nat. d. Pferdes.) 



The superior or internal surface is dee]ily concave from side to side. It bears 

 a central ridge, the spine or "frog-stay" (Spina furcae ungulte), which is high pos- 

 teriorly and subsides abruptly in front. On either side of this is a deep depression, 

 bounded outwardly ])y tlu> rounded ridge formed by the junction of the frog with 

 the bar and sole. This surface presents fine strise and openings for the papillae 

 of the frog matrix. 



The inferior or ground surface presents a central furrow (Sulcus intercruralis), 

 which is bounded by two ridges or crura (Crura furca^ unguhe) ; tlu^se converge 

 and form the apex. 



The sides (Facies medialis et lateralis) are united at the upper })art with the 

 bars and soUs but are free below and form the central wall of the dee]) lateral 

 furrows (Sulci cruroparietales) , which are bounded outwardly by the bars. 



The base is wide and high. It is depressed centrally and prominent at the 



