GENERAL OBSERVATIONS 69 
There can be no doubt that the quantity of fluid brought 
by the bloodvessels of these papille to the foot acts largely 
as a means of hydraulic protection to the soft structures.* 
In like manner as that delicate organ, the brain, is best 
protected by being floated upon the cerebro-spinal fluid and 
bloodvessels (which fluids transmit waves of concussion or 
pressure through the organ without injury to the delicate 
cells forming it), so, in like manner, does the extreme 
vascularity of the foot protect the cells of its softer struc- 
tures from the effects of pressure and concussion. 
That this law of hydraulics may operate in the horse’s 
foot to the best advantage, the veins must be provided with 
valves, and valves of no mean strength. These we know 
to be absent. It is here that the lateral cartilages and the 
‘elastic substances of the coronary and plantar cushions 
step in to supply the deficiency. 
At the time when weight is placed upon the foot (with, 
of course, a tendency to drive the blood upwards in the 
limb), and, therefore, the time when a valvular apparatus 
is needed to retain the fluid in the foot, we find the want- 
ing conditions supplied by the pressure outwards of the 
plantar cushion compressing the large plexuses of veins on 
each side of the lateral cartilages, to which plexuses, it will 
be remembered, the bulk of the venous blood from the foot 
was directed. A more perfect valvular apparatus, auto- 
matic and powerful, it would be difficult to imagine. 
E. GROWTH OF THE HOOF. 
We will conclude this chapter with a few brief remarks 
on the growth of the hoof. That the rate of growth is 
slow is a well-known fact to every veterinarian, and it will 
serve for all practical purposes when we state that, roughly, 
the growth of the wall is about } inch per month. This 
rate is regular all round the coronet, from which it follows 
that the time taken for horn to grow from the coronary 
* The Veterinary Record, vol. iii., p. 518. 
