PHYSIOLOGY OF THE CIRCULATION. 117 



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stream would in the first instance pass from the 

 wide to the narrow portion of a conical tube, and 

 subsequently from the narrow to the wide part of 

 a similar tube. Under these circumstances, a copious 

 effusion occurred through the glass tube commu- 

 nicating with the first portion of the pipe, and an 

 active absorption through that leading to its second 

 division. 



Exp. 5. The perforated membranous tube used 

 with the apparatus described under Experiment 2, 

 being held horizontally in the open air, and slightly 

 pressed at one point, effusion occurred through the 

 lateral apertures behind that point, while numerous 

 globules of air entered those situated nearer to the 

 escaping jet. 



It will, I trust, now be considered as proved, that 

 the active power employed in the animal body for 

 the performance of absorption resides in the currents 

 of blood which incessantly traverse the veins and 

 terminating portion of the capillaries. This opinion, 

 like that of Magendie, rests upon the fact of the 

 permeability or porosity of the walls of the smaller 

 blood-vessels ; but it differs from his in withdrawing 

 the substances placed in contact with those pores 

 from the sole control of powers with which we are 

 not well acquainted, and in substituting for the 

 latter the more general and intelligible cause of fluid 

 motion ; viz., unequal pressure. 



I agree with Sir D. Barry in thinking that the 

 relative vacuum formed within the thorax durino- 



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the act of inspiration, greatly assists the process of 

 absorption. But I contend that it does so indirectly 



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