LETTERS TO BROTHER JOHN. 205 



mach, the ganglionic system, the liver, bowels, &c. 

 &c. all the organs concerned in the nutrition of 

 the body. There is congestion of the brain : the 

 veins of this organ do not carry away the black 

 deteriorated blood with sufficient expedition ; they 

 (the veins) become distended ; and thus, occupying 

 more room than they ought to do, exert a very 

 considerable degree of pressure upon the surround- 

 ing parts the origin of nerves, &c. But, besides 

 the great evil resulting from this general pressure 

 on, and within the brain, there is another evil pro- 

 duced, by the accumulation of venous blood in the 

 brain, equally important. For it is a well-ascer- 

 tained fact, that this black venous blood has a direct 

 influence in diminishing contractility and sensibility 

 it is even capable of utterly destroying them : it 

 is at open war with life it exercises a destructive 

 and paralyzing influence on the living powers, and, 

 wherever it accumulates, poisons the life of the part. 

 Comparing the human machine to a watch, and 

 contractility and sensibility to the elasticity of the 

 main-spring, upon which the motions of the watch 

 depend, then, I say, venous blood has a positive 

 and direct influence in weakening this elasticity; 

 and the several actions constituting life are injured 

 by congestion of venous blood, as the movements 



