i8o 
ON THE ERGOT OF EQUIDAE. 
And now I should like to ask the theorists who affirm that the Callosity 
and Ergot are rudimentary Pads the following cjuestion. "Why are the 
Papillae and hornified conditions of the hornified organs, the Callosity and 
Ergot of the horse, which to-day are useless to their possessors, more develop- 
ed than that of the pad of the cat and dog which is still a useful organ to its 
possessor.? " 
If the Callosity and Ergot are rudimentary pads, the histological struc- 
ture of the Papillae should be the same as, or similar to, that of the pad. 
The rudimentary pad theorist might perhaps say that the pad of the 
horse had been in a more developed state than that of the dog and cat, but 
when the histological structure of the F"rog is observed the Papillae are fouad 
to be less developed than in the Callosity and Ergot and the tops do not 
penetrate the Prickle Cell layer but are merely enveloped by it, precisely 
similar to that of the pad of the dog and cat. 
From this I infer that the Ergot and Callosity were formerly digits and 
that the Frog of the hoof is a rudimentary ball. 
Professor Zietzmann in the "Morphologie, Genese und Bedeutung von 
Kastanie und Sporn der Equiden", published his opinion that the Callosities 
and Ergots of P2quidae are rudimentary pads, thus supporting Ewart's and 
Hinntze's theory. His histological and embryological investigations were 
very extensive and in opposition to the rudimentary toe theorists he wrote 
(page 12) : 
"The histological structure of hoof, claw and nail have quite another 
characteristic, and even the peculiarity that a prominent mass (hoof, claw, 
nail) composed of horn cells and closely bound to the underlayer is thrown off 
from the place of its origin over a wide surface of the cutis vera before it 
appears with its distal edge. This characteristic procedure affects such organs 
in the same manner as a stamp, heavily pressed would, so that it appears 
quite distinctly in the most rudimentary stages. I am thinking especially of 
the hind claws of ruminants and particularly of some kinds of deer, which 
are very little developed but which clearly show the aforesaid growth ten- 
