SCHIN. YOSCHIDA 179 
full development of the Papillae. Such well-developed Papillae are not found 
in the Pad and other common skins. That the histological structure of the 
Ergot resembles that of the Callosity has already been declared by Professor 
Ellenberger and other zoologists. Professor Zietzschmann and others have 
said that the Ergot and the Callosity are rudimentary pads. If this were the 
case, their histological structure should be the same as, or at least be similar to, 
that of the Pad. This resemblance I have not been able to find in my studies, 
and therefore believe that the Ergot and the Callosity are rudimentary digits. 
That, by means of histological and embryological studies, I find the 
Callosity to be a rudimentary degit, I have already explained in "Archiv fuer 
wissenschaftliche und praktische Tierheilkunde", Band 39, Heft 6, 1903 ; 
from which I will only repeat the most important points for the sake of 
clearness. At that time I proved my opinion from Papillae in all grades of 
development. These I have divided into four periods : 
1) In this stage the Papillae have a flat outline, very little waved, and 
are found in less developed skin as the hornified tissues in a very 
early stage. 
2) In this stage the Papillae are cone-shaped. These are found in the 
sole pad of the cat and dog. 
3) In this stage the Papillae penetrate other layers and reach the horni- 
fied surface. These are found in the Horn of a three month's calf 
and in the Callosity of a full grown horse. 
4) In this stage, fully developed and secondary Papillae are found, of 
very complicated form, as can be seen in the Hoof and Claw. 
Thus the hornified tissue can be distinguished according to the grade of 
development of the Papillae. Now let us see to which grades the Papillae 
of the Callosity, Ergot and Pad belong. 
As I have written in 1913, the Papillae of the Callosity belong to the 
third grade of development. After still further research I am in a position 
to declare that the Papillae of the Ergot belong to the third grade and those 
of the Pad to the second grade of development. 
