LETTERS TO BROTHER JOHN. 201 



quence of the other. From this it follows, that the 

 degree of velocity and vigour with which the hloocl 

 flows through the body, during inaction, is proeter- 

 naturally diminished : one of the essential means 

 destined to propel it has been withdrawn; and a too 

 languid circulation is a necessary result. But, as 

 during that increased rapidity of circulation conse- 

 quent on exertion there is also an increased secre- 

 tion and excretion of perspiration and pulmonary 

 halitus ; so, when the circulation is languid, these 

 are deficient : and as these are separated from the 

 blood, so, when they fail to be separated, the greater 

 must be the volume of blood remaining. Thus 

 one of the principal natural means for reducing the 

 blood's volume being removed, there must be ac- 

 cumulation somewhere ; and as the larger arteries 

 are not permanently dilatable while the veins and 

 capillary arteries are so, this accumulation or con- 

 gestion must take place in the veins and capillary or 

 hairlike arteries. 



The blood is propelled through the ultimate 

 tissue chiefly by the power of the heart and large 

 arteries, acting upon the blood, as it were, from 

 behind. When the power of these, therefore, is 

 but feebly exerted, it is manifest that the blood will 



not be driven through the ultimate tissue with the 

 K 3 



