ANATOMY AND PHYSIOLOGY OP THE HORSE^S FOOT. 395 
ment cells (the corpuscles pigmentaires , corpuscles puncti- 
formes of Gurlt and Chauveau), and am of opinion, notwith- 
standing the strong evidence of certain authorities, that they 
are very scarce, particularly at some distance from the coronet 
or secreting surfaces. Indeed, in pulling the villi out of the 
horn-tubes we find them covered, not only with cells, but, 
should the horn be black, also with fine dark-coloured 
granules. 
Not unfrequently this colouring matter is diffused •in irre- 
gularly shaped granular masses, which are thickly clustered 
together in the black horn, the numerous particles of each 
mass not being enclosed apparently in any cell-wall. These 
collections are most abundant, as might he supposed, in the 
cortical lamellae of the fibres, especially those towards the 
outer surface of the wall. They offer a black, brown, or 
brownish-yellow hue, and in many specimens appear as 
narrow elougated particles, disposed in a longitudinal manner, 
as in the horny lamina ; concentrically, as in the walls of the 
fibres ; and irregularly, as in the interfibrous spaces. 
Professor Gourdon* does not believe in the existence of 
pigment-granules or corpuscles in the hoof, and imagines its 
dark colour to be due to a general and deeper tint of the 
fundamental horny substance in the dark than the white 
horn. This idea is readily disproved by making a thin 
transverse section of a white-and-black hoof at the point 
where the shades meet ; the presence of granules in the one, 
and their absence in the other portion ; their abundance in the 
deep-coloured horn, and diminished quantity in the grey, is 
easily demonstrable. Specimens of this kind are shown in figs. 
18 and 23. The first exhibits the dark pigment permeating 
the inner layer of wall-fibres and laminae, and abruptly ter- 
minating, leaving the remainder of the horn of a pale yellow 
tint, while the second offers some streaks of grey penetrating 
the white, the tint being due solely to these tiny black 
particles. 
While the horn cells exhibit the most beautiful play of 
colours by polarised light, the pigment-granules dissemi- 
nated among them suffer no change of hue. 
Another proof of the presence of this pigmentary matter, 
as well as of its power of resisting ordinary decomposing agen- 
cies, is to be found in the circumstance that black hoofs, 
steeped for many months in water, become softened and 
pulpy, and the superficial horn cells more or less broken up 
and dissolved ; but on the surface of the horn, and even in 
the water, the colouring matter is seen floating about like a 
* ‘ Journal des Veterinaires du Midi, 5 vol. viii, p. 389. 
