PHYSIOLOGY OF THE CIRCULATION. 97 



diminished pressure existing within the thorax 

 during the act of inspiration. 



It would be tedious to enumerate the different 

 failures which I experienced in constructing an 

 apparatus in which all these conditions should be 

 observed. The following arrangement is that which 

 proved most effectual ; and the conditions under 

 which the absorbing stream here acted appear to 

 correspond very closely to those affecting the minute 

 currents contained within the veins. 



Exp. 2. The oesophagus of an ox, which formed 

 a convenient membranous reservoir, was suspended 

 vertically, and to its lower extremity was fastened a 

 glass tube, fifteen inches long and one-fourth of an 

 inch in diameter, the lower end of which was re- 

 curved, so that its orifice also looked directly upwards. 

 The extent of tube involved in this curve was 

 not above three inches, the length of the ascending 

 portion being one inch. To the orifice of the latter 

 was then fastened a piece of the small intestine of a 

 fowl, which formed a membranous tube two inches 

 long and about one-third of an inch in diameter ; the 

 other end of this flaccid tube was then attached to 

 the short arm of a glass syphon one-third of an inch 

 in diameter, the arms of which were respectively an 

 inch and a half, and two inches and a half, long 

 (Fig. 2). 



The lower part of the descending, and the whole 

 of the curved, portion of the first glass tube, the 

 entire extent of the membranous tube, and the short 

 arm of the syphon, were then placed in a glass 

 vessel six inches deep, on the rim of which the 



H 



