PHYSIOLOGY OF THE CIRCULATION. 93 



tion the yielding walls of the small blood-vessels, 

 and the minuteness of the pores through which 

 absorption occurs. This view of the process of 

 absorption is moreover sufficiently refuted by one of 

 the author's experiments. Thus he remarks that if 

 the communicating tube be introduced into the 

 femoral vein of a dog or horse, and pushed no 

 further, then the inspiration will produce no effect 

 on the fluid in the cup ; because the relative vacuum 

 in the thorax can be filled from the veins nearer to the 

 chest. * This latter remark, and the admission that 

 the operation of this partial vacuum within the tho- 

 rax does not extend so far as the femoral veins, 

 appear to be quite fatal to this view of absorption. 

 And even if it could be shown that the expansion of 

 the thorax exerts a direct influence on the passage of 

 blood through the smaller veins, the immense dis- 

 proportion existing between the area of the latter 

 and that of the minute absorbing pores situated in 

 their walls, would necessarily cause that influence to 

 be exercised chiefly on the fluid contained within the 

 larger tubes. His other experiments, in which the 

 application of cupping-glasses over poisoned wounds 

 prevented the action of the poison, cannot, in their 

 physiological bearings, be considered as proving more 

 than that an obstruction to the circulation through a 



O 



part prevents absorption a principle which has also 

 been fully established by many other observers. It 

 is now some time since the idea first occurred to me, 

 that the same power of raising from a lower level, 

 and drawing with it an external stagnant fluid, 



* Op. cit., p. is. 



