548 



JiSTHESIOLOGY. 



jDart of the lateral surfaces of the bars and the frog are deep 

 triangular hollows, called the comndssures of the frog. The 

 base or posterior extremities constitute the Iteeln or hidhs of the 

 frog ; these are two round flexible and elastic eminences, formed 

 by the two extremities, and separated by the cleft. They cover 

 the two angles of inflection of the walls, and are continued round 

 the external part of the superior surface of the wall in the form of 

 a band, which is the coronary frog hand; it is from the inferior 

 border of this that the thin covering of the hoof is continued. 

 The summit or toe of the frog is the anterior 

 pointed portion, which is inserted into the 

 narrow j)art of the notch in the sole. 



HORN TISSUE. 



of the hoof presents a flbrous 

 very distinct in the wall, less so 



The horn 

 appearance, 



in the deep-seated parts of the sole and frog, 

 and scarcely traceable in the suj)erficies of 

 the sole, where there is a continual disintegra- 

 tion or separation of the horn in layers more 

 or less extensive. It consists of minute 

 cylindrical tubes or fibres, which have a direc- 

 tion obliquely downwards and forwards, and 

 are arranged in parallel rows, forming layers, 

 placed one over the other, and internally 

 lamellie or plates, the whole united together 

 by an amorphous or intertubular substance. 

 Besides the fibres, plates, and intertubular 

 substance, there is always more or less /ji(/- 

 mentary matter, which consists of colour-cells 

 distributed amongst the concentric plates or 

 layers forming the walls. The horny fibres of 

 the sole have the same obliquity as those 

 of the wall, are secreted from the villi on 

 and finally united to the wall round the 



outer circumference ; they receive a few villi from the inferior 



extremity of each sensitive lamina. 



The horn of the frog differs considerably from that of both 



wall and sole. The tubes are much finer and softer, and have a 



flexuous arrangement. They are united to those of the walls at 



Fig. 213. 

 Ti'ausverse section of 

 the lioru of the wall 

 magiiifted. a, Periople ; 

 b, Horn tissue ; c c, Horny 

 lauiiiife ; d d. Sensitive 

 laminre 



the sensitive sole. 



