LETTERS TO BROTHER JOHN. 29 



waste pipes, carry the deteriorated, dirty, and, if I 

 may so speak, dead and useless blood, from every 

 point of the body, back to the heart. The arteries, 

 arising by one large trunk from the heart, become 

 smaller and smaller as they pursue their course 

 towards their termination in the veins. The veins, 

 arising from the innumerable terminations of 

 arteries, become larger and larger as they proceed 

 towards the heart. The arteries, therefore, in the 

 neighbourhood of the heart from which, as I have 

 just said, they all arise by one common root (the 

 aorta] are large and few; but from the sides of 

 these there are perpetually given off smaller and 

 smaller branches ; while, from these smaller, others, 

 still smaller than they, are continually separating; 

 and so on, until the whole are finally lost in indis- 

 tinguishable minuteness. 



While the arteries are in this state of wonderful 

 attenuation, their course is exceedingly tortuous ; 

 they recoil upon themselves ; and are circumflexed 

 hither and thither, until there is scarcely a point 

 in the body which is not occupied by one of these 

 little vessels. After having thus permeated the 

 universal body, they lose the characteristics of 

 arteries, and assume the structure of veins. The 

 terminations of arteries, therefore, are the beginnings 



