MUSCULO-SPIRAL OR RADIAL PARALYSIS 149 



state of flexion, whilst the limb is rested on the toe. This is due to the 

 relaxation of the triceps extensor cubiti in the case of the elbow, whilst 

 the flexor of this joint (/>., biceps) is not affected. In the case of the 

 knee, fetlock, and interphalangeal articulations the extensors, which are 

 placed in front of the limb, are relaxed, whilst the flexors, which are 

 placed posteriorly, are active. 



The extensors of the shoulder, of which the chief is the supraspinatus, 

 are not affected, and this joint is kept in a state of extension. 



The relaxation of the large head of the triceps lets the summit or 

 the olecranon process down to a lower level, and hence we get the name 

 " dropped elbow," applied to the affection. If an attempt be made to 

 move the animal in a forward direction violent contractions of the 

 supraspinatus and biceps muscles will be noticed in the attempt to drag 

 the limb forwards. But the animal is unable to extend the remaining 

 joints, so that the limb remains resting on the toe with the sole of 

 the foot in view, and if any attempt be made to place weight upon the 

 limb the animal collapses. 



If assistance be rendered by forcing the extension of the knee, 

 fetlock, and interphalangeal joints so that the plantar surface of the foot be 

 placed upon the ground, it will be found that the limb will now support 

 the body. 



The characteristic attitude in which the limb is held will be readily 

 understood if we consider for a moment the action of the extensor 

 metacarpi magnus and the extensor pedis muscles. When these muscles 

 contract, the effect on the limb is to extend the carpal, fetlock, and 

 interphalangeal joints, and when these joints are in a condition of 

 extension the long axis of the large metacarpal bone is brought almost in 

 a straight line with that of the radius, whilst the distal end of the 

 suffraginis, when the extensor suffraginis and extensor pedis attain their 

 highest degree of contraction, is drawn forwards so that the long axis of 

 this bone forms an obtuse angle with that of the large metacarpal bone, 

 the enclosed apex of this angle being directed forwards. A similar 



