THE FOOT 



659 



laminae, or laminellae, first fully described by Fleming.* The number 

 of these depends on the depth of the primary lamina, but they may 

 be from 60 to 120 in number. It is quite common to find some of 

 the secondary laminae bifurcate. The appearance presented on hori- 

 zontal section is very characteristic, and has been aptly likened by 

 Chauveau to a feather, the barb of which is represented by a lamina 

 and the barbules by the secondary laminae. The function of the 

 secondary laminae has been a fruitful source of discussion. 



The Origin of the Horn Laminae. — No one doubts that the wall 

 grows from the coronet, but great controversy has taken place over 

 the origin of the horn laminae, some saying they grow like the wall 

 from a part of the coronary cushion, and others affirming that they 

 obtain their origin from the sensitive laminae. If we were to judge 



Fig. 224. — The Hoof removed, and the Vascular Wall seen from the 



Side. 



1, The periople groove ; 2 and 3, the wall -secreting body ; 4, the bulb of the 

 plantar cushion, richly covered with papillae, and running into 3, with which 

 it joins ; 5 and 6, the sensitive laminae ; 7, increase in size of the periople 

 groove at the heels, where a soft horn is formed, which plasters over the 

 junction of the various foot tissues which here meet. Note that the plantar 

 cushion is below the level of the heel of the pedal bone and lateral cartilage. 



solely by the result of pathological processes, we should say the 

 sensitive secreted the horn laminae ; but Moellerf points out that the 

 sensitive and insensitive laminae are never in actual contact, and that 

 between them are placed the secondary laminae of both varieties 

 (Fig. 225B) . Therefore he argues that the vascular cannot secrete the 

 horn laminae, but that the secondary vascular secrete the secondary 

 horn laminae. If a portion of wall be removed experimentally and the 

 vascular laminae exposed, in the course of a short time the part be- 

 comes covered with a layer of horn, with laminae on its inner surface, 

 and this has been used as a strong argument in favour of the secre- 

 tion of horn laminae from sensitive laminae ; but the horn which is 



* In 1840 W. C. Spooner, op. cit., wrote : ' The inner edges of the laminae 

 appear fimbriated, like the edge of a fine-tooth comb.' 

 f Op. cit. 



