LETTERS TO BROTHER JOHN. 203 



but even for some way along the beginning's of the 

 veins. But when the propelling power from behind 

 that is, the power of the heart and larger arte- 

 ries is not sufficiently energetic, the circulation 

 through the elementary tissue is so slow, that the 

 blood loses its vermilion hue and arterial characte- 

 ristics before it has reached the extremities of the 

 hairlike arteries; and thus that part of the tissue 

 which ought to be filled with arterial blood is 

 gorged only with venous blood, from which the 

 proper secretion necessary to the nutrition of the 

 body cannot be separated, either in due abundance, 

 or of a healthy quality. All that blood which, under 

 exertion, is driven to the surface of the body, to 

 the skin, to the muscles, and along the superficial 

 veins, is, during inaction, sleeping and creeping, in 

 muddy and sluggish currents, along the tortuous 

 and delicate vessels composing the ultimate tissue of 

 the internal organs impeding their action, dis- 

 tending their coats, and oppressing their sensibility. 

 The whole circulating system may be divided 

 into three portions : The heart, and large arteries, 

 whose office is merely to convey the blood to the 

 elementary tissue; the elementary tissue itself; 

 and the large veins, whose office is merely to convey 

 the blood back to the heart. Now, the principal 



