FUNCTION OF THE VALVES. 113 



the ventricles the latter valves are shut, the former open. 

 Each half or side of the heart, through the action of its 

 valves, may be Fij og * 



compared with a 

 kind of forcing 

 pump like the 

 common enema- 

 syringe with two 

 valves, of which 

 one admits the 

 fluid on raising 

 the piston, but 

 is closed again 

 when the piston 

 is forced down ; 

 while the other 

 opens for the es- 

 cape of the fluid, 

 but closes when 

 the piston is 

 raised, so as to 

 prevent the re- 

 gurgitation of the 

 fluid already 

 forced through it. 

 The ventricular 

 dilatation is here 

 represented by 

 the raising-up of 

 the piston ; the 

 valve thus admit- 

 ting fluid repre- 

 sents the auriculo- 

 ventricular valve, 

 which is closed 



Fig. 36. Diagrams of valves of the heart (after Dalton). 



