PHYSIOLOGY OF THE CIRCULATION. Ill 



sorbing power without necessarily entering any kind 

 of pipe ; for it is merely necessary to bring the 

 orifice of the connecting tube in contact with any 

 part of the surface of the stream, inasmuch as the 

 absorbing power exists throughout the whole extent 

 of the moving column. A strong blast of air, 

 directed across the orifice of the tube, caused a 

 similar ascent of the coloured liquid in the other arm. 



Now if, instead of an open jet thus made to sweep 

 across the orifices of a great number of tubes held at 

 right angles to it, we suppose a similar current of 

 liquid to flow along a vessel the walls of which are 

 perforated by innumerable small apertures, it can 

 then be readily understood that the stream, in cross- 

 ing the orifices of all these minute lateral tubes, will 

 exercise the same power of drawing through them 

 any stagnant fluid with which they may commu- 

 nicate externally. In this point of view, the pores 

 situated in the coats of the smaller blood-vessels 

 may be regarded as so many minute short tubes, the 

 internal orifices of which are directed nearly at right 

 angles to the streams of blood, and the external 

 orifices of which are in contact with the various 

 substances absorbed. 



The statement that all moving masses possess the 

 power of inducing a corresponding movement of the 

 fluid particles immediately surrounding them being 

 thus capable of direct proof, it now only remains to 

 be shown that the entrance of an external fluid into 

 the interior of a tube traversed by a rapid stream 

 depends upon a diminution in the amount of pressure 

 acting on the internal surface of that tube. 



