6 PASSAGE OF LIQUIDS THROUGH 



The portion attraction. It is in the highest degree worthy of 



of water not 



chemically notice, that this water, not chemically combined, 



combined, 



has the seems to have the greatest share in the properties 

 share in the which these animal substances possess in the fresh 

 of the tis- state, for the pressed tendons and yellow ligaments 

 become transparent; the former lose their flexi- 

 bility, the latter their elasticity ; and if laid in 

 water, they recover these properties perfectly. In 

 the pores of a porous substance, the fluid molecules 

 are retained by two kinds of attraction, namely, by 

 the affinity which is exerted between the walls of 

 the pores and the molecules of the fluid, and by the 

 cohesion which acts between the molecules of the 

 fluid itself. It would appear as if the molecules of 

 water were thus brought into different states, and 

 this seems to be the cause of the differences ob- 

 served in the properties of these animal substances 

 when they contain different proportions of water. 

 Pressure If the wide opening of the tube, Fig. 1, 



required to 



cause water be tied over with a portion of bladder, 



and other -,- f 



liquids to and water poured into the wide part of 



pass 



through the tube as far as the mark a, we shall 



membranes. , , , . 



find that, when mercury is poured into 

 the upright narrow part of the tube, to 

 a certain height, the whole external 

 surface of the bladder becomes covered 

 with minute drops, which, if the column 

 of mercury be made a few lines higher, 

 unite so as to form large drops. These 

 continue to flow out uninterruptedly, 

 if mercury be added so as to keep the a. 



