70 



THE PROTECTIVE STRUCTURES OF THE FOOT. 



sensitive frog. Immediately in front of the point of the sensi- 

 tive frog they mingle with and are lost amongst the similarly- 

 formed papilla^ of the sensitive 

 sole. It is these rows of papilhe 

 on the inferior surface of the foot 

 which produce the bars. From 

 their union with the papilhe of 

 the sole (compare fig. 43) it will 

 be clear that the bars and sole are 

 structurally continuous, a point to 

 which we shall later refer. The 

 convex form of the coronary band 

 depends partly on a considerable 

 thickening of the cutis (see fig. 



Fig. 42.— Horn-secretiuopapilljcfromthe 41, C, SCCtiou of the COrium), which, 

 coronary band ; magnified. . ^ i • • j • t- • , , 



at this point, is very nrm in texture, 

 indeed of almost cartilaginous consistency ; partly, however, 

 from the richness of this region in blood-vessels (see fig. 36, B). 

 The coronary band produces the central portion of the horny 

 wall. 



3. The Sensitive Lamina.. 



(Figs. 40, 41, d, and 43, a.) 



The corium below the coronary band presents a very different 

 structure from that above. Certain portions become thinner 

 (compare with section in fig. 41), and the tissue shows, instead 

 of papillse, a large number of parallel closely-packed leaves, 

 which extend in straio'ht lines from above downwards and 

 forwards. These leaves are termed the sensitive lamina. 

 The portions of the cutis bearing such leaves may be col- 

 lectively termed the sensitive wall. 



The sensitive wall covers the anterior surface of the pedal 

 bone and the lower portion of the lateral cartilages. Towards 

 the back of the foot the two sides approach the middle line, 

 forming an acute angle, and are inclined towards each other 

 from above downwards. At the heels the sensitive wall of 

 either side is sharply reflected forwards at an acute angle with 

 its former course, and lying between the papillce of the sensitive 

 sole and those of the reflected coronary band (already described), 

 forms a strip about 1 to 1^; inches wide, which secretes the 



