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A TEXTBOOK OF PHYSIOLOGY 



stand the vertical side tubes A to E. R is a resistance introduced by 

 means of a wide tube filled with small glass marbles. Y is a 

 rubber tube of equal calibre to X leading to the rigid tube Z, similar 

 to X. The amount of fluid flowing to the tube can be regulated by 

 the clamp K. Further, the fluid can flow from the tube X to the 

 tube Z either by Y when the clamp L is shut and clamp I/ 1 open, or 

 by the tube E when the clamp L l is shut and clamp L is open. 



When there is a free flow from W (K open), and free communica- 

 tion by Y from X to Z (L closed, L 1 open), it will be seen, according 

 to the resistance introduced by clamp M , the coloured fluid rises in 

 all the side tubes to a nearly equal extent, gradually decreasing 

 from A to J. When the clamp L 1 is slightly closed, the fluid rises 

 higher in tubes A to E than before, and falls in tubes F to J. The 

 same thing is seen if the fluid, instead of passing by Y, is sent through 

 E, which better exemplifies the circulation. 



PIG. 87. SCHEMA TO SHOW THE FLOW IN RIGID AND ELASTIC TUBES. (Marey.) 

 The compressor should compress the single tube not the double tube, as figured. 



In this schema the flow has been through rigid tubes. The same 

 Jaws which have been discussed in connection with rigid tubes obtain 

 in elastic tubes if the flow of fluid be continuous. 



If the inflow be intermittent, in the case of the rigid tube, the whole 

 column of fluid is driven on, step by step, by each stroke of the pump, 

 and the outflow is intermittent. In an elastic tube, on the other hand, 

 if the resistance to the output has been made great, as by constricting 

 the orifice, the elastic wall of the tube is extended by the input 

 of the pump, and the elasticity of the wall comes into play, and con- 

 tinues the output after the stroke of the pump has ceased, so that the 

 flow becomes continuous. 



This is shown by the schema (Fig. 87)- Here the coloured water 

 flows from a head of pressure through two tubes 1 metre long, and 

 of the same bore; but one tube is rigid, the other elastic. The 

 outflow orifices are also of the same size. 



