LAMINITIS AND NAVICULAR DISEASE. 
699 
separation of the sensitive and horny laminae, a slight exuda¬ 
tion filling up the spaces so caused, descent of the os pedis 
at the toe, flatness and convexity of the sole, lameness, in¬ 
flammation of the bone, ostitis, absorption of the margins of 
the bone, and, as the disease advances, extension of the 
absorption over the whole plantar surface. That undue weight 
will cause this, is borne out by the fact that in cases where 
one foot or limb is violently injured, and the animal com¬ 
pelled to bear his weight upon the opposite foot; you have 
laminitis, more or less severe, often as a result. The bone 
now participating in the morbid action, we find that the can¬ 
cellated tissue—and we have little else in the coffin-bone— 
undergoes a great change; the Haversian canals dilate or 
become opened up, and the result of this enlargement is the 
conversion of the contiguous canals into one cavity, hence 
the increased porous appearance of the os pedis in chronic 
laminitis, an appearance which you evidently think gives the 
disease the characteristics of mollities ossium. I maintain 
that this is not at all analogous to degeneration of organs 
from malnutrition, or from any undefined change within the 
bony tissue itself primarily, but simply through an alteration 
of the structure of the soft parts from the causes above 
described, viz., great weight of carcase, over-exertion, want 
of exercise, undue paring or rasping weakening the horny 
support of the animal; for in reality the horn and laminae 
are the true weight-supporters. The coffin-bone cannot bear 
any direct weight upon itself. 
You state that the subject of laminitis is almost certain to 
be exempt from any tendency to formation of bone-spavin, 
sidebones, ringbones, splint, &c. I can only state that your 
experience and observations are different to mine, as I find it 
associated with all sorts of exostoses, and the specimens I 
have that show the most extraordinary changes in the os 
pedis through absorption, are combined with very large 
sidebones. 
NAVICULAR DISEASE. 
I think that the pathology of this lameness is easily under¬ 
stood. Professor Dick has taught, and still teaches, what I 
conceive is the simplest yet grandest solution of a problem 
that has puzzled many earnest and able inquirers. His 
teaching is indelibly impressed upon my mind, and had he 
done no more toward the advancement of veterinary surgical 
pathology than investigating this disease alone, the profes¬ 
sion is under a heavy tribute of gratitude to him. He says, 
