ANGEIOLOGY. 95 



former pierces the interosseous ligameut, and inosculates with the external 

 malleolar ; the latter spreads its branches on the outer side of the heel and 

 of the foot. 



The interned plantar artery proceeds along the internal side of the sole, 

 and inosculates with the adjacent vessels. The external plantar, much the 

 larger, passes forward as far as the fifth metatarsal bone ; it then crosses the 

 metatarsus, and joins the anterior tibial, to form the plantar arch. 



PI. 135, ßg. 15 ', sartorius muscle, cut off; '', hole in the tendon of the 

 adductor magnus ; ', femoral artery ; ', superficial epigastric ; \ profunda 

 artery ; ^'' ^', perforating branches of the profunda ; °, internal, '•*, external 

 circumflex arteries; "''% superficial pudic ; ", poplita^al artery. Fig. 17 \ 

 anastomotica ; ', anterior tibial ; ^ recurrent branch ; ', external, \ internal 

 malleolar; % tarsal vessels; ', metatarsal vessels; 'an artery of the toes. 

 Fig. 16, plantar arteries : \ posterior tibial artery ; '■', internal, ', external 

 plantar arteries ; \ deep plantar arch ; \ a branch to the back of the foot. 

 % a metatarsal artery ; ', its division into two branches ; *, union of two such 

 branches ; \ division into the arteries of the toes ; '", union of two such 

 divisions ; ", vascular plexus at the tip of the toes. 



3. The Veins. 



The veins commence in the capillary system, and are therefore continu- 

 ous with the arteries : in some parts they appear to arise out of a cellular 

 or spongy intermediate structure, although this may be nothing more than a 

 venous plexus. From the origins the veins unite and form larger branches, 

 ■which ultimately end in two great trunks. Both small and large veins are 

 remarkable for their numerous anastomoses, and large veins are often seen 

 to divide and unite again. 



Veins are composed of the same number of coats as arteries, but . the 

 middle lamina is much thinner, therefore they collapse when empty or when 

 divided. The external or cellular coat is similar to that of arteries ; the 

 middle or fibrous coat wants the external elastic lamina, but possesses the 

 two other layers of contractile fibres, the external circular and the internal 

 longitudinal ; the third, or innermost, or serous coat is stronger, but similar 

 to that of the arteries, being, indeed, continuous with it through the capilla- 

 ries on the one hand, and the cavities of the heart on the otlier. The most 

 striking peculiarity in this tissue is seen in the presence of numerous semi- 

 lunar folds or valves; each of these is composed of a duplicature of the 

 membrane, inclosing some fibrous cord. Their concave floating end is 

 towards the heart, and therefore the blood in its course towards this organ 

 meets no resistance from the valves, while they present serious obstacles to 

 its reflux. These valves are sometimes in pairs, sometimes single; they are 

 most numerous in the extremities and in the deep veins, and are generally 

 found at points of confluence ; they are absent in very small veins, and in 

 the large trunks, as the cavae, iliacs, internal jugular, and innominata j also 

 in the cerebral veins, and in the whole of the portal system. 



ICONOGRAPHIC EKCVCLOP^DIA. — VOL. II. 51 801 



