V)34 LECTURE V. 



The veins freely communicate with one 

 another, and joining together, they form 

 tubes of apparently larger dimensions, but 

 of less actual calibre than the branches by 

 which they were formed ; so that in these 

 vessels the blood is obliged to pass through 

 converging channels, which eventually end 

 in the two vense cavse, the conjoined areae 

 of which qre inconsiderable when compared 

 with the space the blood has occupied in all 

 the minute veins of the body. Consequently, 

 if the heart pumps out an ounce and a half 

 of blood at each action into the arteries, 

 and the same quantity is returned, in the 

 same time, to that organ by the veins, it 

 must be urged in the like interval from the 

 small arteries into the veins, and run with 

 accelerated velocity as it approximates to 

 the heart. Of this circumstance we may, 

 I think, be convinced by ocular demon- 

 stration, even in the ordinary practice of 

 our profession. There is much more space 

 in the veins than in the arteries, which pre- 

 vents any trivial obstruction in the former 

 channels from impeding the transmission 

 of the blood into them through the latter. 

 The superficial veins which meander on 



