GENERAL OBSERVATIONS 51 
aspects, giving a section of a lamina the appearance of 
being studded with papille. We have already pointed out 
the ridge-like formation of the human nail-bed, and noted 
that, with the exception that the secondary ridges are not 
so pronounced, it is an exact prototype of the laminal 
formation of the corium of the horse’s foot. 
The distribution of the lamine over the foot we have 
discussed in the chapter devoted to the grosser anatomy. 
In a macerated foot the sensitive lamine of the corium 
interdigitate with the horny lamine of the hoof; that is 
to say, there is no union between the two, for the simple 
reason that it has been destroyed; they simply interlock 
like the unglued junction of a finely dovetailed piece of 
joinery. But no further, however, than the irregularities 
of the underneath surface of the epidermis of the skin can 
be said to interlock with the papilla of the corium does 
interlocking of the horny and sensitive lamine occur. It 
is only apparent. The horny laminex are simply beauti- 
fully regular epidermal ingrowths cutting up the corium 
into minute leaf-like projections. 
In a macerated specimen, then, the exposed sensitive 
structures of the foot exhibit the corium as (1) the Coronary 
Cushion, fitting into the cutigeral groove; (2) the Sensitive 
Lamine, clothing the outer surface of the terminal phalanx, 
and extending to the bars; (3) the Plantar Cushion, or 
sensitive frog; and (4) the Sensitive Sole. 
The main portion of the wall is developed from the 
nuimerous papille covering the corium of the coronary 
cushion. We have in this way numberless down-growing 
tubes of horn. Professor Mettam describes their formation 
in a singularly happy fashion: ‘ Let the. human fingers 
represent the coronary papille, the tips of the fingers the 
summits of the papille, and the folds of skin passing from 
finger to finger in the metacarpo-phalangeal region the 
depressions between the papille. Imagine that all have a 
continuous covering of a proliferating epithelium. Then 
we shall have a more or. less continuous column of cells 
growing from the tip of the finger or papilla (a hollow tube 
4—2 
