PHYSIOLOGY OF THE CIRCULATION. 101 



able extent of the membranous tube became in this 

 manner exposed, globules of air also passed through 

 its lateral openings, and escaped with the stream. 

 While absorption was proceeding the membranous 

 tube always became flattened, whereas during the 

 occurrence of effusion it appeared distended, and 

 more cylindrical in shape. In this apparatus the 

 absorbing stream flowed almost directly upwards. 

 In other cases, where the membranous tube was 

 placed horizontally in a long shallow vessel, absorp- 

 tion of the external fluid occurred with the same 

 rapidity so long as the same conditions were observed. 



Having, by these experiments, proved that a 

 stream, in passing through a flaccid membranous 

 tube, can exercise an absorbing power, it now re- 

 mains for me to show that in this rude apparatus 

 there are represented the most important of those 

 conditions which are known to affect the currents of 

 venous blood. And these conditions may be con- 

 sidered in the same order in which they were before 

 mentioned. 



1. It is essential to the success of the experiment 

 that the absorbing stream should flow from a narrow 

 to a much wider tube. In this respect there is a 

 marked analogy between the contrivance which 

 repeated failure in these experiments suggested, and 

 that arrangement of the minute veins and the con- 

 tiguous portion of the capillaries by which the 

 streams of blood traversing this part of the circu- 

 lating system are made to operate in a precisely 

 similar manner. For at this point innumerable 

 small rapid streams are, throughout the body, per- 



H 3 



