222 PHYSIOLOGICAL PHYSICS. [Chap. xxi. 



shown that, all other things being equal, an elastic 

 tube is capable of discharging a greater quantity of 

 fluid than a rigid one in the same time. This Marey 

 proved experimentally by means of a Marriotte's 

 bottle (page 210), filled with water, whose outflow pipe 

 was furnished with a cock. From the outflow pipe 

 branched two tubes, one of brass and the other of 

 caoutchouc, both of the same length, both terminating 



* o / o 



in points of the same diameter. To prevent the 

 elastic recoil of the caoutchouc tube causing a back- 

 ward flow of water from it, a valve was placed at its 

 beginning. When the cock was opened, and a con- 

 tinuous flow permitted through both tubes, the quan- 

 tity discharged by both was the same. The continuous 

 action failed, in this case, to develop the elastic re- 

 action of the caoutchouc tube. When, however, the 

 cock was opened and closed intermittently, the quan- 

 tity discharged through the elastic tube exceeded that 

 from the glass tube. The explanation offered for this 

 is, that the slowing of the velocity of the current pro- 

 duced by the elastic distension diminishes the resistance 

 due to friction, and the force that would have been 

 expended in overcoming the resistance is now devoted 

 to furthering the advance of the fluid. 



Thus, the elastic reaction of the walls of tubes 

 diminishes the velocity of the current, but increases 

 the quantity of Jluid discharged. 



CHAPTER XXI. 



THE MECHANICS OP THE CIRCULATION. 



IT is now necessary to apply the laws that have 

 n indicated to 

 the blood-vessels. 



been indicated to the circulation of the blood through 



