82 THE PROTECTIVE STRUCTURES OF THE FOOT. 



soft, tough and light-coloured portion is of some practical 

 importance, as the two sometimes become separated, probably 

 in consequence of their unequal hardness. 



The outer surface of the middle sheath in perfectly normal 

 feet often presents transverse rings which must not be con- 

 fused with those resulting from diseases of the feet. The 

 middle sheath is the chief constituent of the wall, which ex- 

 tends below the sole and forms the bearino- margin of the 

 foot. 



C. The laminal or connecting sheath (tigs. 44, g, 47 and 48, /) 

 is the innermost layer of the wall ; it consists of a large number 

 of closely packed horny laminj^, which cover the inner face of 

 the inner sheath from the lower margin of the cutigeral groove 

 to the horny sole. 



The laminal sheath is moulded on the sensitive lamina:^ and 

 formed by the epithelial cells covering them. The horny 

 laminoe interdigitate with the sensitive lamina?, so that each 

 sensitive lamina is grasped by two horny laminae and each horny 

 lamina by two sensitive laminae. As the inner sheath approaches 

 the bars, its lamina? decrease in length to disappear altogether 

 in the bars themselves (fig. 48,/'), the upper surface of which 

 (corresponding to the middle sheath of the wall) it covers. In 

 freshly stripped hoofs the individual laminae feel smooth and 

 slippery, and can be moved to and fro, but when dry they 

 become stiff and usually assume a wavy contour. In number, 

 course, breadth, etc., they correspond exactly with the sensitive 

 laminae, of which they form the counterpart ; their free borders, 

 therefore, point inwards towards the centre of the foot. The 

 upper end of a horny lamina begins at the lower margin of the 

 cutigeral groove and is slender, as is the lower end (fig. 49, a), 

 which seems to become smaller and to disappear where it meets 

 the sole. Between the horny laminae, at this point, are little 

 holes (fig. 49, h) for the reception of the papillae of the corium, 

 which lie at the lower ends of the sensitive laminae. The 

 diminution in size and disappearance of the horny laminae is 

 only apparent; in point of fact, they preserve their entire 

 breadth between the second sheath of the wall and the horny 

 sole, which parts they unite by means of the horn secreted in 

 their interspaces. This arrangement can readily be verified on 

 vertical section. The horny laminae lying between the wall 



