58 DISEASES OF THE HORSE’S FOOT 
locking of the sensitive and horny lamine. We see that 
the horny lamin are ingrowths of the rete Malpighu, 
ploughing into and excavating the corium into the shape of 
leaves—the sensitive laminez. Putrefactive changes simply 
break into two separate portions what originally was one 
whole, by destroying the cells along its weakest part. This 
part is the line of soft protoplasmic cells of the rete 
Malpighii. Thus the more resistant parts (the horn on the 
one hand, and the corium covering the foot on the other) 
are easily torn asunder. 
As a result of the evidence we have quoted, we are able 
to answer our original question in the affirmative. Seeing 
that the horny and the sensitive lamine are both portions 
of the same thing—namely, a modified skin, in which the 
epidermis is represented by the horny lamina, and the 
corium by the sensitive—it is clear to see that the cells 
covering the inspreading horny lamine are dependent for 
their growth and reproduction upon the cells with which 
they are in immediate contact—namely, those of the sensi- 
tive lamine—and that therefore the sensitive lamine are 
responsible for the growth of the horny. 
B, CHEMICAL PROPERTIES AND HISTOLOGY OF HORN. 
Horn is a solid, tenacious, fibrous material, and its 
density in the hoof varies in different situations. It is 
softened by alkalies, such as caustic potash or soda and 
ammonia, the parts first attacked being the commissures, 
then the frog, and afterwards the sole and wall. Strong 
acids, such as sulphuric acid and nitric acid, also dis- 
solve it. 
The chemical composition of the hoof shows it to be 
a modification of albumin, its analysis yielding water, a 
large percentage of animal matter, and materials soluble 
and insoluble in water. The proportions of these, as existing 
in the various parts of the hoof, have been given by 
Professor Clement as follows : 
7a 
