DEFECTS IN THE GAITS. 581 



In two instances our attention was arrested by the degree of openness of the 

 articular angles. Besides the various forms of chronic arthritis, we have, in other 

 instances, found the tibio-tarsal angles so large that their branches, in their max- 

 imum state of separation, formed almost a straight line. This disposition has 

 appeared to us to have for its effect the augmentation of the spring-like action 

 of the hock. This action, seen in the freshly-dissected articulation, when it is 

 flexed or extended, is the more intensified as the constituting bones of the articu- 

 lation are closer to their limit of separation. As no definite lesion can be dis- 

 covered in horses which are affected with dry spavin, it might be that the sudden 

 and abrupt movement which accompanies, in such cases, flexion and extension 

 of the metatarsus has its sole cause in the mode of coaptation and union of the 

 bones of the leg and of the canon. 1 



It is also possible, as Pastureau has supposed, that the accidental suspension 

 of the internal patellar ligament upon the femoral trochlea, whose internal lip is at 

 times very salient, opposes at first a certain resistance to the movement of 

 flexion of the member, and, as this obstruction suddenly disappears, the flexion 

 is then spasmodically completed. 2 



These are, of course, only hypotheses, but the study .of the nature and cause 

 of this condition will receive ample reward and are well worth one's undertaking. 



All these facts demonstrate that science does not know the exact 

 cause of this remarkable symptom. Be this as it may, the horse 

 which is so affected is not easily relieved ; 3 he has, consequently, lost 

 much of his value, although this does not render him unable to per- 

 form his work, even the most laborious kind. 



2d. Rotating Hocks. Horses of the heavy-draught or the 

 lighter types quite frequently present this outward rotation of the 

 hocks, for which there is no remedy ; they are, as a rule, animals de- 

 generated from hard labor. 



During the walk, and more particularly when the foot is placed on 

 the ground, the point of the hock describes a sort of rotation outward, 

 making the toes converge forward and inward. It is said, in this case, 

 that the horse has rotating hocks. He is not prevented from rendering 



1 G. Barrier, Bulletin de la Societ6 centrale de mtidecine v6t6rinaire. in Recueil de medecine 

 vetSrinaire, ann6e 1882, p. 372. 



2 Another very beautiful as well as plausible theory of the nature of string-halt is that of the 

 excessive elasticity of tjie tibial aponeurosis, particularly of its triangular fasciculus, which extends 

 from the anterior face of the hock-joint to be attached to the tendon of the anterior extensor of 

 the phalanges. When the foot is on the ground, the aponeurosis is tensed: when the foot is 

 raised, it will recoil, like a piece of India-rubber, and impart a sudden movement to the iimb. 

 This disposition is more common in well-bred horses, in which string-halt is, as we have 

 remarked, more frequent. The treatment consists in section of the aponeurosis at the superior 

 extremity of the canon, where this structure can be outlined from the exterior. 



In the camel and the elephant this aponeurosis is composed almost exclusively of elastic 

 fibres, and hence the sudden elevation of the members of these animals. (Harger.) 



3 Boccar has proposed to make section of the tendon of the lateral extensor muscle of the 

 phalanges close to its termination upon that of the anterior extensor. (Journal veterinaire et 

 agricole de Belgique, anne 1845, p. 273.) We have had occasion to perform this operation once, 

 but without result. 



