106 



THE GROWTH OF THE HOOF. 



there can be no sharp margin drawn between the horn pro- 

 duced by the coronary band and that produced by the sensitive 

 laminae. The horn produced by the vascular laminae, however, 

 has a different structure, and bears the impress of the tissue 

 from which it grows. 



The following explanation has been given of the production 

 of horn by the sensitive laminae. Each lamina produces a row 



,/■>"». -- ^ •X'ii. • ■ \ ,. :feV - ■-=^ ^<- /.{ > All' v^x. 



'f:i ith ■s>''-'-\ ■■ML'' * ^' ''>l''j i# ••• •.• ' ■ >^- ^ "■■(;■ '■ •%. F ^^ 



v ■ V ,i 



Fig. 66. — Horizontal section, showing relation of a horny lamina to the corium. A. the 

 horny lamina derived from the cells B, B, which have grown into the corium C. When 

 the horny lamina is withdrawn after macerating the foot, the space it occupied is the 

 cleft between the " fleshy " lamina;, and the processes upon which the lines from B end 

 are then known as secondary laminse. It will be seen that they increase the horn- 

 producing area ; the cellular character of the horny lamina is, however, still evident. 

 (From a micro-photo., Oc. 3, obj. 7.) ^ 



of horny cells on either of its surfaces. The opposing rows of 

 horny cells between each pair of sensitive laminse unite, 

 forming a single horny lamina. Hence each pair of sensitive 

 laminse enclose a horny lamina, and the total number of horny 

 and sensitive laminae is approximately equal. The amount of 

 horn contributed by the sensitive laminae to the middle layer 

 of the wall is extremely small, being confined to a very thin 

 layer of cells secreted by the margins of the sensitive lamiut^e, 



