GENERAL OBSERVATIONS 



55 



tion of the processes is a condensation of the epithelial 

 cells immediately above the rete Malpighii, with a partial 

 or total loss of their nuclei. This is the first appearance 

 of true horn, and its commencement is almost coincident 

 with the first stages of ossification of the os pedis. 



With the appearance of horn comes difficulty of section- 

 ing. The last specimen that Professor Mettam was able to 







ifc 



m^mrm * 











Fig. 29. — Section of an Epithelial Ingrowth from an Equine 



Foetus. 



It shows commencing secondary laminar ridges. In the centre are 

 epithelial cells which are undergoing change into horny elements 

 to form the horncore, or 'horny lamina?' (Mettam). 



satisfactorily cut upon the microtome was from a fcetus be- 

 tween three and four months old. In this the secondary 

 laminar ridges were clearly indicated, and the active layer of 

 the rete Malpighii could be traced without a break from one 

 ingrowing epithelial process to the next, and around this, 

 following all the irregularities of its outline, and covering 

 the branches of the nascent laminae. The laminae mostly 

 show this branching as if a number of different growing 



