668 ANATOMY AND PHYSIOLOGY OF THE HOUSE’S FOOT. 
ance, somewhat like the pile on the very finest velvet. These 
papillae or villi during life incline downwards, and might be 
supposed to be merely the minute conical points seen on the 
surface of the derm in other parts, here enlarged in size and 
increased in number to serve a particular purpose. 
In point of numbers they vary but little over the whole 
surface of the cushion, but their size differs considerably. 
Thus it is that, on the upper parts of the protuberance they 
are seldom more than one third of the length they gradually 
attain as they reach its lower border ; and they maintain this 
increased development to the inflexure at the heels, on the 
parts bordering the sides of the plantar cushion, and do not 
begin to decrease to finer and shorter fdaments beyond these, 
as has been stated. On the contrary, at the lower border of 
the cushion, and at the commencement of the white zone, they 
are largest and longest, and continue so to the bottom of the 
zone. There is no great regularity in their length at any one 
point ; indeed, the greatest diversity prevails with regard to 
their volume, though it may be said that in a medium-sized 
carriage or riding horse’s foot, at the central portion of the 
cushion, they measure from 5-16ths to 7-16ths of an inch. 
The structure of these minute processes, both on the 
perioplic ring, the plantar cushion, and the white zone, 
appears to be somewhat similar to that of the papillae of the 
derm, in so far as the arrangement of the blood-vessels is 
concerned, though they are much more interesting as micro- 
scopical objects. 
In examining one of them by means of a high magnifying 
power, it will be found that it consists of a little bundle of 
exceedingly fine fibrous tissue, derived from that composing 
the cushion, and which, fining off towards the point, forms a 
long tapering body that appears to be covered, like the upper 
surface of the derm, by the extremely thin and translucent 
basement membrane that is supposed to play so important a 
part in the growth and nutrition of the epidermic cells of 
the skin. 
This beautifully fine structureless membrane, which also 
covers the intervillous or interpapillary space, cannot usually 
be distinguished until the numerous horn cells and pigment 
granules that adhere to and cover its exterior to the very 
extremity of each villus (fig 13), are removed. 
The interior of each villus or papilla, when they have 
been injected previously with some transparent coloured fluid, 
and examined in the microscope, is seen to be occupied in 
great part, and for its whole length, by tiny looped prolonga- 
tions from the arteries of the cushion, which are spread out 
