CAUSE OF THE CAPILLARY CIRCULATION. 133 



leaves, no matter whether they take place in the height of summer or 

 just at the close of winter, when the sap first rises, or even in the germ- 

 inating seed which is under the ground, and has never yet been exposed 

 to the light, may, without difficulty, be referred to the nutritive change 

 earned on in the leaves of the plant under examination, or its parent, by 

 the influence of the rays of the sun. 



All this holds good, not only in the nutrition of a cell, the more com- 

 plicated nutrition of the various parts of a flowering plant, or Explanation of 

 even of an animal, but likewise in those destructive changes circuSionof 

 restricted to the latter class, and arising in interstitial decay ; animals, 

 for the blood has a double duty to perform : it not only serves for nutri- 

 tion, but also for the removal of effete and dying parts. These it effects 

 the oxidation of, their carbon passing into carbonic acid, their hydrogen 

 into water ; and this is accomplished by the oxygen which has been ob- 

 tained in the process of respiration. The scarlet or arterial blood, charged 

 with its oxygen, passes to all parts of the economy in search of organic 

 particles ready to be removed; it effects their disorganization, and, becom- 

 ing thereby venous, is pressed onward. And now, if we recall that nu- 

 trition in animals depends on the access of air even fibrin can not arise 

 from albumen except under that condition we can not avoid the con- 

 clusion that all operations of repair and all operations of waste are made 

 to conspire together for the production of movement ; and though every 

 part offers its own special cause, as depending on nutrition, or disente- 

 gration, or secretion, they may be all grouped together as the necessary 

 results of one more primitive operation, which is the supply of oxygen 

 to the blood in the respiratory mechanism. 



In my view of this subject, it is therefore the arterialization of the 

 blood in the lungs which is the cause of the circulation in De en(ience of 

 man. I consider the circulation as the consequence of res- circulation in 

 piration ; and though, in one sense, the minor causes are the res P iratlon - 

 numerous, each portion of nervous material, each muscular fibre, every 

 secreting cell working its own way, these subordinate actions are all 

 referable to one primordial act, and that is the exposure of the blood to 

 the air. 



Whatever, therefore, interferes with respiration, interferes with circula- 

 tion. If an irrespirable gas is thrown into the cells of the lungs, the 

 passage of the blood is instantly arrested, and asphyxia ensues. Or, if 

 the access of the air is cut off, as in drowning, in vain the heart exerts 

 its utmost convulsive throb it is unable to drive forward the Case of res- 

 blood; and in those cases, by no means infrequent, yet un- deathT^" 1 

 doubtedly the most surprising occurring in the practice of drowning. 

 medicine restoration from death after drowning, the whole success turns 

 on one condition, the re-establishment of the arterialization of the blood. 



