208 OUTLINES OF EQUINE ANATOMY. 



tlie anterior vena cava. Along tlie internal surface of the 

 fore limb, in the living animal, we may see a large vein 

 running upwards along the subcutaneous portion of the 

 radius. This is the superficial brachial, cephalic, or 

 plat vein, from which blood is sometimes extracted by the 

 process of venesection ; at the insertion of flexor brachii 

 it sends a branch internally to that muscle to join the 

 humeral vein as above mentioned, but the main portion 

 runs along the groove between this muscle and extensor 

 metacarpi magnus, and proceeding upwards empties its 

 contents into the jugular vein ; opposite the front of the 

 elbow-joint this vessel receives the spiral vein. Now the 

 skin may be removed from the internal surface of the arm ; 

 this may be done by an incision along the central line from 

 the elbow- joint to the lower part of the knee, through the 

 circular horny process or chestnut found opposite the 

 inferior part of the superior third of the radius, and dis- 

 secting the skin backwards and forwards. It will be 

 advisable also to remove the integuments from the outer 

 surface of the limb as low as the knee, if sufficient time is 

 available for examination of both aspects of the arm (other- 

 wise the white fibrous tissue of the outside will become 

 dry and hard by exposure to the air). Thus the aponeu- 

 rotic expansion of pectoralis transversus and panniculus is 

 exposed, it inferiorly gradually blends with the ordinary 

 subcutaneous areolar tissue. By division of it we bring to 

 view the faschia of the arm, a dense layer of white fibrous 

 tissue running round the back of the limb from the outer 

 sharpened border of the ulna to the inner surface of the 

 radius, supero -internally it terminates by blending with the 

 internal lateral ligament of the elbow-joint, and by becoming 

 attached to the point of the ulna, between these two attach- 

 ments it receives the insertion of scapulo-ulnaris. Inferiorly 

 it blends with the annular ligament of the knee, which is 

 nothing more than a thickening of this faschia in conse- 

 quence of the addition to its substance of fibres, some of 

 which run from the inner surface of the radius just above 

 the knee to trapezium, others from the inner surface of the 

 knee obliquely upwards and outwards. From the internal 

 surface of the annular ligament of the knee thick fibrous 

 bands pass to enclose the tendons situated at the back of 

 the knee-joint. The first muscle posteriorly situated to the 

 radius is — 



