148 ON THE NATURE -VXD PRINCIPLES OF 



the manner in which my experiments were pro- 

 ductive of certain effects, but as a peculiar anatomical 

 arrangement evidently connected with, and provided 

 for, an important physiological purpose, it also con- 

 stitutes a powerful argument in favour of the general 

 hydraulic principles, which I have supposed to re- 

 gulate many of the chief uses of the circulation. In 

 the tuft of tortuous capillaries thus protruded into 

 the extremity of each excretory tube, we have but 

 an exaggeration, for a special object, of the general 

 contrivance by which the lateral pressure of the 

 blood contained in the terminating arterial ramifica- 

 tions is maintained at a point sufficient for the 

 occurrence of effusion. It must be observed, that, 

 in the healthy state, the lateral pressure induced by 

 the impediments to the blood's passage through the 

 convoluted vessels merely causes the constant exuda- 

 tion of its more aqueous portion into the surrounding 

 tube. And by reflecting on this arrangement of the 

 blood-vessels, and the natural absence of albuminous 

 matters in the urine, the reader will find no difficulty 

 in understanding the facts and reasoning which tend 

 to demonstrate the connection between an increase 

 in the lateral pressure of the blood contained in 

 those vessels, and an effusion into the urinary 

 passages of its various albuminous constituents in a 

 ratio corresponding to that increased pressure. 



