108 



THE XiROWTH OF THE HOOF. 



bond between the two. The lower ends of the sensitive laminae 

 are provided, however, with horn-secreting papilhe, which again 

 are continuous with those of the sensitive sole, so that in the 

 hoof after removal from the foot they appear merely to be the 

 marginal papilke of the sensitive sole. At the point where 

 wall and sole meet, and between the individual horny laminae, 

 these papilhe and the surfaces between them produce tubes and 

 inter-tubular horn, and thus fill the spaces previously occupied 



^- 



FlG. (57. — t'ross section of the cxMinectiny' sheath of the wall. a. iimeiinust portion of the 

 protective slieath of the wall : tlie horn tubes are seen to extend right up to the liorn 

 haniina; ; b, portion of the vascular wall ; c, portions of horn lamina? connected with horn 

 wall ; d , irregularly developed horn laniinte ; c", the so-called secondary lamina; ; d, 

 sensitive or vascular lamina;; d' , irregularly developed vascular lamina;; e, injected 

 arterial vessels. 



by the sensitive laminae, which would otherwise divide the horny 

 lamina?. The horn thus thrown out connects the lower portions 

 of the laminal sheath with the sole, and assists in forming the 

 " white line " (compare fig. h^). Strictly speaking, therefore, 

 the white line is produced by the sensitive wall alone. The 

 horny lamincC are derived from the lateral surfaces of the sensi- 

 tive lamina^ which, however, they have left behind ; the inter- 

 laminal horn is a later acquisition, being produced by the 

 papilla? which terminate each sensitive lamina, and, like the • 

 horn of the sole, is still in connection with the structure pro- 

 ducing it. 



An interesting point has been raised as to how the coronary 

 papilla? secrete tubes of horn and not solid cylinders. It 

 is, of course, clear that, as the papilla becomes covered with 



