Ill 



arteries and capillaries. The tubes between the pump and 

 the resistance are the arteries ; those on the distal side of the 

 resistance are the veins. The side branch around the bamboo 

 substitutes a wide channel for the narrow ones and is thus 

 equivalent to a dilatation of the vessels. Between the pump 

 and the outlet valve is a side tube leadingf to a membrane 

 manometer which records the changes in the pressure (intra- 

 ventricular) within the pump (the loss in conveying- the pres- 

 sure through the short, wide connecting tubes may be neg- 

 lected). A mercury manometer is placed between the pump 

 and the capillary resistance to measure the arterial pressure, 

 and a second mercury manometer on the distal side of the 

 capillary resistance to measure the venous pressure. 



Fig. 28 



Diagram of valve used in the artificial circulation scheme (W. T. Porter). 

 The inner glass tube is provided with a jacket of rubber tubing. The arrows 

 indicate the direction of the fluid. 



The device used for the aortic valve consists of a small 

 glass tube which is fastened in a large glass tube by a collar 

 of rubber tubing. The small glass tube is closed at one end. 

 One side is pierced with a valve hole. The valve hole is 

 closed by a piece of rubber tubing which is drawn over the 

 small glass tube, and the middle portion of the rubber tubing 

 is cut away except over the hole. During the stroke of the 

 pump the water enters the small glass tube under pressure, 

 lifts the rubber, escapes through the valve hole, and is carried 

 off by the large glass tube. When the pressure in the small 

 glass tube is no longer as great as that in the surrounding 

 large glass tube, the rubber shuts the valve hole. Backflow 

 is thereby prevented. The mitral valve is similar to the 

 aortic, but the position of the small glass tube is reversed. 



362. The Conversion of an intermittent flow 

 INTO A CONTINUOUS FLOW. In a system of tubes with rigid 

 walls, a pump will force a fluid through the tubes in such a 

 way that the inflow and outflow will be equal and in the same 

 time. The outflow ceases the instant the inflow ceases. 



