MECHANISM OF ABSORPTION. 59 



evident in the literal signification of the very word. 

 But so far as my present knowledge extends, all 

 previous theories have referred that power either to 

 the enlargement of the chest in inspiration or to the 

 dilatation of the ventricles. 



Now, while readily admitting the influence of 

 these two actions in facilitating the return of venous 

 blood, and thereby indirectly favouring absorption, I 

 cannot think that they exercise any immediate effect 

 in promoting the entrance of extraneous matters 

 through the coats of the smaller vessels. 



But if, on the other hand, we suppose this suction- 

 power, whatever its precise nature may be, to be 

 caused by and reside in the stream of blood, to be 

 greatest wherever the current of the latter is most 

 rapid, to be increased in its activity by whatever 

 accelerates the velocity, and diminished by whatever 

 induces a retardation, of the circulation through the 

 part, then we shall have a principle of action, at once 

 simple and efficacious, in perfect accord with the 

 established laws of matter, and by the operation of 

 which many morbid and healthy phenomena of the 

 human body can be satisfactorily explained and 

 readily understood. 



In the present stage of the inquiry I shall not 

 attempt to make many applications of this principle, 

 but content myself with briefly alluding to some 

 facts which seem to corroborate the doctrine herein 

 sought to be established. 



o 



Magendie proved that a state of plethora retarded, 

 and one of depletion promoted, absorption. These 

 two conditions of the system are evidently attended 



