GENERAL OBSEEYATIONS 69 



There can be no doubt that the quantity of fluid brought 

 by the bloodvessels of these papillse 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. 



