104 PHYSIOLOGY OF THE CIRCULATION. 



derivative power was much increased, the gravitating 

 column of water in the long arm diminished the 

 pressure within the short arm so much, that the con- 

 tiguous portion of the membranous tube was then 

 forced against the orifice of the latter, so as entirely 

 to close it. And this obstruction to the passage of 

 the stream necessarily caused effusion through the 

 lateral apertures of the membrane. 



This inconvenience attending the employment of a 

 more powerful syphon, would, I conceive, be ex- 

 perienced in a minor degree were the change from 

 a flaccid to a rigid tube more gradually effected, as it 

 is in the animal body. And to test the accuracy of 

 this supposition, I repeated some of the former 

 experiments with a more powerful syphon, having 

 previously fastened to its short arm a piece of 

 caoutchouc tubing half an inch long, and over that 

 a membranous tube six inches in length. Although 

 every other condition was the same as before, this 

 slight alteration of the apparatus, by which the stream 

 was made to pass from the membranous into the 

 caoutchouc tube, and then into the glass syphon, 

 facilitated the action of the latter so much, that a 

 very rapid absorption of the external fluid occurred, 

 though the lateral apertures in the membranous tube 

 did not approach within three inches of the termina- 

 tion of the caoutchouc tube. 



In explanation of this point, it may also be re- 

 marked, that though the derivative power exercised 

 by the act of inspiration arises from the same im- 

 mediate cause as that by which a syphon acts, viz. 

 diminished pressure within the several recipient 



