184 Movement of Microscopic Particles f April, 
explanation must take into account the remarkable pheno- 
mena of ele( 5 tric osmose investigated by Wiedemann. 
It was first observed by Porret that when the poles 
of a battery are placed in two portions of water separated 
by a porous division, not only is some of the water decom- 
posed, but another and far larger portion is impelled towards 
the negative pole. Wiedemann found that for 1 part of 
water decomposed, 5000 parts were transported through the 
porous septum. This impulsion is greater as the eleCbric 
resistance of the liquid is greater, and ceases altogether 
when sufficient acid or salt is added to render the liquid a 
good conductor. There is an obvious analogy to the cir- 
cumstances of pedesis, except that the energy is derived not 
from the septum, but from a cell. If these surmises should 
prove corredt the phenomenon of pedesis will acquire great 
importance, because it was believed by Graham and others 
that osmose plays a large part in the functions of life, pro- 
bably causing the motion of sap in plants and of juices 
through the walls of animal cells and vessels generally. It 
is certain that the solutions of gum, albumen, &c., which 
permeate the vessels both of animals and plants, are gene- 
rally well fitted for the production of pedesis. From this 
point of view it is much to be desired that the inquiry 
should be extended, so as to include the relations of organic 
particles to solutions both of salts and of organic substances. 
I hare hardly been able to enter upon this part of the sub- 
ject. The motion of particles of gamboge has already been 
mentioned, and other organic paints, such as sepia and 
indigo, give like results. The yolk of an egg rubbed up in 
water showed intense pedesis. These motions are far from 
being prevented when the medium is a solution of albumen, 
gum, glycerin, gelatin. Some experiments seemed to show 
that, in the presence of these organic substances, small 
quantities of acid or alkali would not prevent pedesis. 
Observations of this kind duly extended might have a most 
important bearing upon many motions, such as that of 
cyclosis observed in vegetable cells, or even upon the 
whole subject of the motion of fluids in vegetable and 
animal organisms. I tried a few experiments with the sap 
of a tree, and found that gamboge rubbed up with it gave 
a perfectly boiling appearance. Other organic mediums — 
such as alcohol, ether, amylic alcohol, chloroform, spirits of 
turpentine, wood spirit, &c. — seemed to arrest pedesis ; but 
they ought to be much more carefully tried with different 
suspended particles, and in mixtures of different proportions 
with water. 
