66b 



A MANUAL OF VETERINARY PHYSIOLOGY 



thu secreted is derived from the secondary vascular laminae, and 

 no one contends that these secrete the primary horn laminae. The 



following explanation appears to be 

 the correct one : The horn laminae 

 are secreted from the lower edge of 

 the coronary body ; here protoplasmic 

 cells are poured out between the 

 papillae ; these cells are carried down 

 with the wall, being pressed into and 

 moulded between the sensitive leaves, 

 thus becoming horn laminae, the exact 

 counterpart in shape of the mould 

 in which they are made. All this 

 occurs in the region marked 3, Fig. 

 223. As the wall grows down the 

 horn-leaves are carried with it, so 

 that there is a perpetual movement oc- 

 curring between the slowly travelling 



Fig. 225A. — Horizontal Section 

 of the Hoof and Vascular 

 Tissues at the Anterior 

 Part of the Horse's Foot 

 (Moeller). 



a, Bony tissue of the os pedis ; b, 

 stratum periostale ; c, stratum 

 vasculosum ; d, sensitive laminae; 

 e, secondary laminae, or lamellae ; 

 /, primary horn laminae ; g, wall 

 of the hoof, with its horn fibres. 



Fig. 225B. — Horizontal Section of 

 Portion of a Pair of Lamina : 

 (1) Sensitive, (2) Horny, each 

 with their Lamellae. 



The laminae and lamellae have been 

 pulled apart ; the protoplasmic cells 

 which separate the lamellae of each 

 type are partly represented. The 

 figure shows that these cells come 

 between both primary and secon- 

 dary laminae of each series, which 

 are therefore never in actual contact. 

 It is from these protoplasmic cells 

 that the horn lamellae are secreted. 



insensitive and the fixed vascular laminae. The rate of this move- 

 ment is probably about 0*0125 inch in twenty-four hours, on the 

 assumption that the wall grows § inch in the month. During the 



