358 ^4 Manual of Veterinary Physiology. 



the elastic nature of the horn, the existence of large elastic 

 cartilages at the posterior and lateral part of the foot, and the 

 fact that though the internal foot is a solid mass anteriorly, 

 yet it is soft and yielding posteriorly. 



The amount of movement occurring in the foot under the 

 influence of the body- weight increases no doubt with the 

 velocity at which a horse may be travelling ; it is very small 

 at the walk, and still less when he is made to throw all his 

 weight on to one foot by lifting up its fellow. But even with 

 this simple test special and delicate instruments are capable 

 of registering the movement, and, moreover, of measuring it. 

 I cannot here enter into a description of the apparatus em- 

 ployed ; that used by Lungwitz is fully described,* also 

 that employed by myself, f 



There is no difficulty in seeing the movement imparted 

 to a column of rluid circulating in these parts ; for if we 

 divide a plantar vein, and make the horse walk, eveiy time 

 the foot comes to the ground expansion occurs, and the jet 

 of blood is considerably increased, and when the foot is 

 taken off the ground the jet of blood becomes reduced. 



We must accept it, therefore, as a proved fact that the 

 venous circulation is largely facilitated by the expansion 

 and contraction of the posterior part of the foot — during 

 expansion the blood being driven upwards, and during con- 

 traction the veins relaxing aspirate the blood into their 

 interior. 



So perfect are these changes that there are no valves in 

 the veins of the foot, and none are found until near the 

 middle of the pastern. To assist the circulation, the large 

 venous trunks at the postero-lateral part of the foot are in 

 close connection with the lateral cartilages, and some pass 

 through its substance. 



Sensitive Laminae. — We have now to consider the means 

 by which the weight of the body is supported within the 

 foot. It is universally recognised that this is carried out 

 by the union of the horny with the sensitive lamina'. That 



* The Journal of Comparative Pathology and Therapeutics, vol. iv. 3. 

 f The Veterinary Record, January, L892. 



