,^2 ON TIIK F.KGüT OF EQUIDAE 
clear that as the fore Callosities are not foot-rests neither can the liind ones be. 
If the Callosities are toe-rests, the ancestors of these families must, at 
tlie time when they were still plantigrades, have possessed them, but, so far 
as I know, no Ungulata was ever a sole-walker with all its limbs. 
L) tlckker has studied the Tarsal glands of reindeer and said that these 
corresponded with the Callosities of the horse and that the Ergots arc rudi- 
mentary toes. 
Ludwig P^-ank, in "Handbuch der Anatomie der Haustiere", second edi- 
tion, page 796, has written on the microscopic structure of the Ergot and 
Callosit)', that these form rudimentary horntubes and laminae. 
Ellcnberger, Stoss, Bonnet and many histologists have stated in their 
handbooks that the Ergot is of the same histological structure as the Callosity, 
that it is possible that the Ergot may be a rudimentary digit but that this 
has not been proved. 
In 1 91 3, when I wrote "Morphologische und Physiologische Bedeutung 
der Sogenannten Kastanie an den Gliedmassen den Equiden", my research 
into the matter of the Callosity had been thorough but I had made little his- 
tological observation on the Ergot. I had only made a macroscopical (ob- 
servation of the position and said that it might be a rudimentary pad. 
In 1914, Zietzmann wrote in "Morphologie, Genese und Bedeutung von 
Kastanie und Sporn der Equidae", that from many deep microscopic, macros- 
copic and embryological researches he had concluded that the Callosity and 
Ergot are rudimentary pads. 
Since that time, to determine whether the Ergot, like the Callosity, is a 
rudimentary digit or, on the other hand, a rudimentary pad, I have made 
further investigaticjn which I shall now describe in the following order: 
J .) Microscopic and Macroscopic Observations of the Ergot. 
2. ) Histological comparison of the Ergot and Pad. 
3. ) My own opinions on the subject. 
I obtained material for observation from the slaughterhouse of Halle a.S 
by the kind favour of Professor Haeckel ; first, fresh material preserved in 
