PART PLAYED BY THE LAMINi-E. 107 



and collected in the interspace between two horny laminae. 

 All the rest of the cells go to the formation of horny 

 laminae. 



Henle {Das Wachsthum des menschlichen Nagcls unci des 

 Pferdehufs, Gottingen, 1884, p. 32) says, " In my opinion the 

 laminae of the sensitive wall correspond to the folds of the 

 corium in the human nail-bed. The horny laminae correspond 

 to the stratum mucosum of the nail, and between the two 

 structures there is only this difference, that in man the 

 stratum mucosum and the horny layer are shar23ly differentiated 

 from one another, whilst in the horse the horny laminae and 

 the horny wall insensibly coalesce. From this fact I conclude 

 that in man the body of the nail glides forward over the 

 deeper structures without taking up new elements, whilst, as 

 in the hoof the horny laminae and wall are intimately connected, 

 it seems quite possible that the wall may receive additions 

 from the laminae. That this increment is very slight however, 

 is shown by the fact that the wall remains of equal thickness 

 throughout any vertical line." (For cut of human nail-bed, 

 see p. 61.) 



The horny laminie produced by the sensitive wall are 

 gradually thrust or carried by the downward growth of the 

 horny wall towards the ground, remaining, however, in un- 

 broken continuity with the middle sheath of the wall, and, 

 as a whole, representing the inner sheath. On the ground 

 surface of the hoof thev form the white line. Normal cppowth 

 of the wall essentially depends on a normal condition of the 

 sensitive and horny laminae. The layers of cells formed 

 by the latter may be regarded as permitting the gradual 

 downward movement of the horny wall, and as preventing 

 its quitting its proper direction. Such an explanation is 

 strengthened by the existence of a l^emarkable peculiarity in 

 the formation of the horny laminae, which will later be de- 

 scribed. 



The firm connection between the laminal and middle sheaths 

 of the wall, and the interdigitation of the horny and sensitive 

 laminae, explain the intimate connection between the horny and 

 sensitive walls, but not that between the hornv wall and sole, for 

 the laminal sheath, which in its continuous downward progress 

 projects beyond the laminae, would not of itself form a sufficient 



