118 THE MECHANICAL FUNCTIONS OF THE FOOT. 



hoof when bearing weight, never occurs in a normally formed 

 and sound hoof. 



2. The hoof dilates, or at least becomes tense, at the 

 moment of greatest dorsal flexion* of the fetlock, along the 

 entire coronary border, but not along the bearing margin. On 

 the contrary, at this moment the posterior part of the hoof 

 " rotates " on the bearing surface, especially the angle of 

 the bars and the walls of the heels, together with the other 

 tissues lying between them, whilst the wall and sole of 

 the anterior half of the hoof move towards the middle line, 

 that is, the hoof becomes narrower below at the moment when 

 the anterior half of the bearing surface is under the greatest 

 strain. 



3. The sole does not sink at the moment indicated, the bars 

 and portions of the sole next them rather rising and approaching 

 one another laterally. The sole, therefore, presents a narrower 

 and not a wider appearance. 



4. The limbs of the frog are not thrust asunder at the above- 

 named moment, that is, broadened and pressed backwards, but 

 are pressed together, thickened from the sides, and their length, 

 as a whole, increased, the under portions of the bulbs being 

 drawn somewhat backwards and outwards. 



5. This rotary movement in the hoof occurs both above and 

 below synchronously and isochronously, that is, simultaneously 

 and at equal periods of time. 



Lechner's results, which are entirely supported by those of 

 Gierth, introduced new views as to the physiology of the horse's 

 hoof, and at the same time gave rise to fresh experiments. 

 Lungwitz and his assistant (now Oberroszarzt a. D. H. Schaaf) 

 made experiments on living hoofs in regard to dilatation of the 

 hoof at the bearing surface, using a specially constructed 

 instrument. The dilatation of the bearing border during the 

 period when the hoof carries weight is shown in the following 

 table : — 



* It will be noted that the fetlock joint may be flexed in a forward direction 

 (dorsal flexion), as during the last phases of movement, preparatory to the foot 

 leaving the ground. Dorsal flexion of the fetlock is sometimes, though perhaps 

 less precisely, described as " extension.'' Flexion backwards (volar flexion) takes 

 place during movement of the limb through the air, and is the condition most 

 often indicated, in this country, by the term "flexion.'' 



