6 THE SURGICAL ANATOMY OF THE HORSE 



Behind the gracihs is another elevated area due to the underlying 

 semimembranosus muscle. 



Running obliquely upwards and forwards across the gracilis is the 

 internal saphena vein, a vessel of large calibre which is formed by the 

 union of the upward continuations of the outer and inner metatarsal 

 veins. It dips in between the sartorius and gracilis about the junction 

 of the upper and middle thirds of their line of apposition, and empties 

 itself ultimately into the femoral vein. The application of pressure 

 will cause the vessel to be raised, when its course becomes much 

 more evident. It is occasionally adopted as a seat for the operation 

 of venesection. 



In front of the saphena vein is the saphena artery, a long and slender 

 vessel which follows the course of the vein, and divides into two 

 branches which accompany the outer and inner roots of the saphena 

 vein. 



Anteriorly placed to the saphena artery again is the internal saphena 

 nerve. This arises from the anterior crural nerve at the brim of the 

 pelvis, and emerges from between the sartorius and gracilis with the 

 artery and vein. It will be further dealt with in the chapter on nerves. 



The slight depression which indicates the position of the interstice 

 between the sartorius and gracilis should be carefully examined, 

 particularly in its upper part, which is the situation of the deep 

 inguinal lymphatic glands. In this region the glands cover the under- 

 lying femoral vessels, and they become very evident in cases of 

 lymphangitis. 



If the hand be now passed down the inner aspect of the limb, it 

 will be ascertained that the inner surface of the tibia is immediately sub- 

 cutaneous, and it will also be found that the subcutaneous bone is widest 

 above and gradually tapers as we descend. Manipulation of this part 

 is of importance in the diagnosis of deferred fracture, of which particular 

 injury the shaft of the tibia is the most common seat. 



The very important region of the hock is next to be considered. 



