PHYSIOLOGY OF THE CIRCULATION. 95 



compressible for rigid tubes (by assimilating the 

 conditions of the observations to those known to 

 exist in the living body) removes the chief, and, in 

 my opinion, the only valid objection to this explana- 

 tion of the function in question ; 



And conclude this part of my communication by 

 endeavouring to elucidate the physical principles on 

 which the action of absorption depends. 



Exp. 1. A piece of the descending aorta of a 

 horse, which formed a flexible yielding pipe, nearly 

 cylindrical in shape, four inches long and one inch 

 in diameter, was fastened horizontally to the lateral 

 opening of the reservoir. Having previously closed 

 all its collateral branches, with the exception of one, 

 I fitted into the latter the short arm of an arched 

 glass tube, the long -arm of which dipped into a 

 vessel containing coloured liquid. The internal 

 orifice of the pipe was somewhat contracted in 

 fastening it to the opening in the reservoir, so that 

 its calibre at this point would be less than that of 

 the rest of the pipe. During the passage of the 

 stream through the latter, the coloured liquid rose in 

 the glass tube, and on increasing the height of the 

 impelling column the vessel containing the coloured 

 liquid was speedily emptied. The outer orifice of 

 the glass tube being then allowed to communicate 

 freely with the external air, the jet issuing from the 

 pipe instantly assumed the pulsating character ; at 

 the same time that the entrance of air into its 

 interior caused a gurgling sound. 



It now only remained to be shown that a stream 

 traversing a flaccid membranous tube possesses the 



