CHAPTER V. 



THE BLOOD-VESSELS AND NERVES OF THE FOOT. 



Between the bones, ligaments, tendons, and elastic tissues on 

 the one side, and the protective structures of the foot on the 

 other, lie a number of organs, which, though not perhaps of the 

 same importance in a mechanical sense as those already 

 reviewed, nevertheless exercise a paramount influence in the 

 play of such phenomena as growth, nourishment and sensation. 

 These organs are the blood-vessels and nerves. 



A. BLOOD-VESSELS. 



The blood-vessels are a system of membranous tubes which 

 convey the blood from the centre of circulation to all parts of 

 the body, and return it thence to the heart. As the blood, on 

 which the growth and nourishment of the entire animal body 

 depends, is continually moving, it is clear that the same tubes 

 which conduct it from the heart cannot return it there. For 

 this reason two varieties of blood-vessels are distinguished — 

 those coming from the heart, termed the arteries, and those 

 going to it, the veins. 



With few exceptions, the arteries can be distinguished from 

 the veins in the dead as well as in the living subject. They 

 have thicker walls, are of less calibre, and fewer in number 

 than the veins. In the dead body they seldom contain blood, 

 while the veins are more or less filled. Before Harvey's dis- 

 covery they were supposed to carry air ; hence their name. If, 

 in a living animal, a large artery be pressed on with the linger, 

 a regularly-repeated light beat (the pulse) can be felt. If 

 such a vessel be opened, bright red blood issues in a jerking 

 stream. The veins exhibit no pulsation ; their blood is dark red, 

 and escapes from the severed vessel in a steady flow. 



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