i82 THE SURGICAL ANATOMY OF THE HORSE 



spond to the branches of the axillary artery, and at the entrance to the chest 

 it joins the jugular veins and the axillary vein of the opposite limb to 

 form the anterior vena cava. Occasionally the prehumeral vein empties 

 into the subscapular vein instead of into the brachial. 



THE LYMPHATICS 



The lymphatic vessels vary considerably in size. The largest very 

 much resemble veins, but their coats are much thinner and the valves 

 more numerous, a fact which gives the vessels a " beaded " appearance. 

 In the smallest lymphatics or lymphatic capillaries the walls are made 

 up of a single layer of epithelial cells which are elongated. In a medium- 

 sized vessel we have a lining of pavement epithelium the cells of which 

 are elongated in the direction of the vessel's axis. More outwardly we 

 find muscular fibres disposed in a circular manner and others disposed 

 obliquely. Even the smallest lymphatic vessels do not, therefore, com- 

 municate openly with the interstices in the connective tissue. 



The vessels are more numerous than the veins, the course of which 

 they follow closely. In dealing with the veins we found, speaking 

 generally, that they could be divided into two sets — namely, those placed 

 very superficially, which were much the largest ; and those more deeply 

 seated, which followed the course of the principal arteries ; and a some- 

 what similar division may be applied to the lymphatics. 



The lymph from the foot is carried by vessels which follow the 

 course of the digital and metacarpal veins. Thus we find, in cases of 

 septic infection of the foot such as suppurating corns, gathered nails, in 

 some cases of quittor, &c., the infection quickly spreads up the limb 

 and a swelling appears along either side of the flexor tendons. 



The lymphatics again differ from veins, inasmuch as in certain 

 places they aggregate together and form glands. These are usually 

 somewhat kidney-shaped, having a fibrous and mubcular tramework 



