888 THE SENSE ORGANS AND SKIN OF THE HORSE 
ridges, which subside in front and are fused with the sole; they are united with each 
other by the frog. For topographic purposes the wall may be divided into an an- 
terior part or ‘toe’ (Paries ungule dorsalis), medial and lateral parts or “ quar- 
ters’ (Paries ungulee medialis, lateralis), and the angles or “ heels” (Anguli parie- 
tales). It presents two surfaces and two borders. The external surface is con- 
vex from side to side and slopes obliquely from edge to edge. In front the angle of 
inclination on the ground plane is about 50° for the forelimb, 55° for the hind limb; 
on the sides the angle gradually increases and is about 100° at the heels. The curve 
of the wall is wider on the lateral than on the medial side, and the slope of the medial 
quarter is steeper than that of the lateral one.! The surface is smooth and is crossed 
by more or less distinct ridges, which are parallel with the coronary border and 
indicate variations in the activity of the growth of the hoof. It is also marked by 
fine parallel strize, which extend from border to 
, border in an almost rectilinear manner and in- 
dicate the direction of the horn tubes. 
The internal surface is concave from side to 
side, and bears about six hundred thin primary 
lamine, which extend from the coronary groove 
to the basal border of the wall. Each bears a 
hundred or more secondary laminz on its sur- 
faces, so that the arrangement is pennate on 
cross-section. These horny lamine are continued 
on the inner surface of the bars, and dovetail with 
corresponding laminze of the the corium. The cor- 
onary border (Margo coronarius) is thin. Its outer 
aspect is covered by a layer of soft horn known 
as the periople (Limbus corneus); this appears as 
a ring-like prominence above and gradually fades 
out below; at the angle it forms a wide cap or 
bulb and blends centrally with the frog. The 
inner aspect of the border is excavated to form 
the coronary groove (Sulcus coronarius ungul), 
which contains the thick coronary corium. The 
Fic. 710.—Dicrr or Horse, SHowinc gyoove is deepest in front, narrows on the sides, 
Scurrace RELATIONS OF BONES AND : . . 9 : 
Jornts. Tue Cantiacris Lancery &20d is wide and shallow at the heels.? It is per 
Exposep. forated by innumerable small, funnel-like openings 
a, First phalanx; b, second phalanx; which are occupied by the papille of the coronary 
¢, third phalanx; d, cartilage; ¢, distal sesa- Goriym in the natural state. Between the border 
moid or navicular bone; f, pastern joint; 
@, coffin joint; h’, cut edge of wall of hoof Of the wall proper and the periople there is a small 
();% laminar corium, (After Ellenberser, — groove which contains the corium of the periople. 
in Leisering's Atlas.) : - 5 ; ¢ 
At the heel this groove is merged with the coronary 
groove. The basal or ground border (Margo basi- 
laris) of the unshod hoof comes in contact with the ground. Its thickness is greatest 
in front and decreases considerably from before backward on the sides, but there is 
a slight increase at the angles. Its inner face is united with the periphery of the 
''The slope of the wall varies considerably in apparently normal hoofs. Lungwitz found 
by careful measurements of 56 fore and 36 hind feet the following average angles: 
Fore Foor Hinp Foor 
WOCeccumetreal seater oe Beenie {robe 54.1° 
Medial angle... .. ; : 25 LOME5 42 96.5° 
Lateral angle... .. : Scand OL37° 96.1° 
angle of 60°. The length of the wall at the toe, quarters, and heels is in the ratio of about 3:2:1 
> The wide groove af the heels, however, contains chiefly the corium of the periople. 
