Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins
Todd, Robert Bentley
greater ease and more rapidity than pure water. 
This may be added to the facts set forth already 
to prove, in the most decided manner, that the 
greater power of permeation manifested by one 
of the two fluids in experiments on endosmosis 
does not follow from any greater viscidity it 
may possess than the fluid opposed to it. In 
sixteen parts of water I dissolved two parts of 
sugar and one part of oxalic acid. In this so¬ 
lution I plunged the reservoir of an endosmo- 
meter, closed with a piece of bladder, and filled 
with pure water : this did not show any diffe¬ 
rence of level in the tube during the two hours 
that I continued the experiment. There was 
consequently no endosmosis. Nevertheless, I 
found that the water contained in the endosmo- 
meter contained a large quantity of oxalic acid, 
whether tested by the addition of lime-water 
or by the palate, which last also detected the 
presence of sugar. Thus the sweet-sour fluid, 
exterior to the endosmometer, had penetrated 
the water contained within its cavity. If this 
circumstance was proclaimed by no increase in 
the volume of the water, this undoubtedly was 
owing to the included water having lost by the 
descending counter-current an amount exactly 
equal to the amount it had gained by the in¬ 
ward or ascending current. There was no en¬ 
dosmosis in the sense in which I use that word, 
although it is certain that there were two active 
antagonist currents athwart the membrane which 
separated the two fluids. It must not be lost 
sight of that I only give the title of endosmosis 
to a stronger current opposed to a weaker 
counter-current, antagonists to each other, and 
proceeding simultaneously athwart the septum, 
dividing the two fluids which are made the 
subjects of experiment. The instant these two 
antagonist currents become equal, there is no 
accumulation of fluid on one side, and there is 
then no longer any effort at dilatation or im¬ 
pulsion; in a word, there is no longer any 
The opposite directions in which the endos¬ 
mosis towards water, effected by acids of deter¬ 
minate density, and the endosmosis from water 
occasioned by other fluids, would lead us to 
conclude that in placing such a fluid as gum- 
water or sugar-water in an endosmometer fur¬ 
nished with an animal membrane, and in con¬ 
tact externally with an acid solution of appro¬ 
priate density, we should have a much more 
rapid endosmosis towards the included fluid 
than if it were pure water in which the endos¬ 
mometer was plunged ; and this in fact is what 
I have found to be the case by experiment. 
Into an endosmometer, closed with a piece of 
bladder, I poured a solution of five parts of 
sugar in twenty-four parts of water. Having 
plunged the reservoir of the instrument into 
water, I obtained in the course of an hour an 
ascent of the included fluid, which may be re¬ 
presented by the number 9. The reservoir of 
the same endosmometer filled with a portion of 
the same saccharine solution, having been 
plunged into a solution of oxalic acid, the den¬ 
sity of which was 1.014, (3.2 parts acid to 100 
solution,) I obtained in the course of an hour 
an ascent of the included fluid, which required 
to be represented by the number 27. The 
substitution of a solution of oxalic acid for 
pure water consequently caused the amount of 
endosmosis in the same interval of time to be 
tripled. 1 obtained like results with the tarta¬ 
ric and citric acids, employed of the densities 
required to enable them to produce endosmosis 
towards water. From these experiments it 
would appear that water, charged with a small 
proportion of one of the acids, of which men¬ 
tion has been made, possesses a power of pene¬ 
tration athwart animal membranes greater than 
that inherent in pure water. But a direct ex¬ 
periment, detailed in an earlier part of this 
paper, proves that this is not the case; pure 
water used by itself is still the fluid that pos¬ 
sesses the greatest power of penetrating through 
animal membranes. If, consequently, in those 
experiments which I have last described, the 
water charged with acid passed more readily 
and more copiously into the saccharine solu¬ 
tion than pure water, this happens undoubtedly 
from other causes or conditions which I cannot 
take upon me to explain, but which appear to 
be : 1st. A reciprocal action between the two 
heterogeneous fluids, an action which modifies, 
which even completely inverts the natural 
power of penetration possessed by each of the 
fluids when employed singly ; 2d. A particular 
action of the membrane upon the two fluids 
which penetrate it, an action which, with the 
animal membrane, gives the stronger current 
or current of endosmosis to the acid solution of 
due density, and the weaker current or coun¬ 
ter-current of exosmosis to the pure water. It 
seems to me impossible to deny this peculiar 
action to the animal membrane, when we see 
that a vegetable membrane in the same circum¬ 
stances produces endosmotic phenomena di¬ 
rectly the reverse. The peculiar influence of 
the membranous septum is likewise manifested 
in a very striking way in the experiment in 
which I have shown that the current of endos¬ 
mosis flows from water towards alcohol when 
these two fluids are divided by an animal 
membrane, and, on the contrary, that the cur¬ 
rent of endosmosis flows from alcohol towards 
water when the two fluids are separated by a 
membranous septum of caoutchouc. 
Endosmosis, in the present order of things, 
is a phenomenon restricted to the realm of or¬ 
ganization ; it is nowhere observed in the inor¬ 
ganic world. It is in fact only among organ¬ 
ized beings that we observe fluids of different 
density separated by thin septa and capillary 
pores ; we meet with nothing of the same kind 
among inorganic bodies. Endosmosis, then, 
is a physical phenomenon inherent exclusively 
in organic bodies, and observation^ teaches us 
that this phenomenon plays a part of the high¬ 
est importance in their economy. It is among 
vegetables especially that the importance of the 
phenomenon strikes us ; I have, in fact, de¬ 
monstrated that it is to endosmosis that are 
due, in great part, the motions of the sap, and 
particularly its very energetic ascending motion. 
I have also shown that all the spontaneous mo¬ 
tions of vegetables are referable to endosmosis. 
The organic vegetable tissue is composed of a


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