ENDOSMOSE 



bladder-like bodies ; and with a bladder may be shown on a large scale 

 what is done by them on a small. 



If a bladder be partially filled with water holding salt or sugar in 

 solution, have the orifice closed tight, and be put into a basin of 

 water, it will be found after a time that the bladder will become filled 

 and distended ; water has been absorbed through the tissue. While 

 it is thus with the bladder, if the remaining water in the basin be 

 examined it may be found to have acquired the peculiar taste of the 

 salt or the sugar of which a solution was introduced into the bladder 

 before its immersion ; or if the taste be not perceptible, an appli- 

 cation of appropriate chemical tests will show that there is such salt 

 or sugar there in solution. Apparently there must have been a 

 transference of water from the outside into the inside of the bladder, 

 and a transference of a lesser portion of the solution of salt or sugar 

 from within to the water without in the basin ; apparently this can 

 only have taken place through the tissue of the bladder ; and all 

 that is known of the process goes to prove that it is not only so to 

 appearance but that it is so in fact. To these two distinct operations 

 the designations Endosmose and Exosmose have been given by 

 Dutrochet, a French physiologist ; and these designations have come 

 into general use in treatises on the subject in our own and other 

 languages, Endosmose being applied to the passage of pure water, or 

 of weaker solution, or a solution of other matters, from without, and 

 exosmose to the passage of the water with matter in solution from 

 within. 



Reasoning from a widely extended analogy, it is thus that the 

 moisture is imbibed, absorbed, or, to speak more guardedly, trans- 

 ferred from without into the interior of the cell. 



In consideration of this process being the initiative of phenomena 

 of vegetation on which the alleged meteorological efi'ects of forests 

 depend, it may be well to ascertain, as satisfactorily as we can, how 

 it is that what takes place is effected, that we may carry with us a 

 definite conception of this radical operation in our subsequent con- 

 sideration of subsequent operations to which attention must be given. 



Without entering on the question how matter is held together, I 

 may call attention to three manifestations of the attractive force : 

 that of cohesion, whereby particles of the same substance are held 

 together, as in a piece of wood, a drop of quicksilver, or a drop of 

 water; adhesion, whereby particles of one substance adhere to 

 another substance, as water, treacle, or tar adheres to the finger 



