Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit25760/108/
ENDOSMOSIS. 
100 
through the capillary conduits of the plate, and 
this flow would have become perceptible by 
the sinking of the water in the tube, the inte¬ 
rior of which was only two millimeters in dia¬ 
meter. 
The result of this experiment was that the 
plate of marble, which was four centimeters in 
diameter, did not lose by filtration, in one 
day, more than the small quantity of water 
capable, by its subtraction, of lowering its 
level one millimeter and a half in the tube. 
I next tried syrup in this endosmometer, the 
reservoir being plunged into pure water ; but 
no endosmosis was induced. I now reduced 
the thickness of the plate of marble to one 
millimeter and a half; in this state it lost by 
filtration, in the course of a day, eleven mil¬ 
limeters of water measured by the tube. The 
permeability of this plate was, as may be per¬ 
ceived, very sensibly increased : still the en¬ 
dosmometer which it closed when filled with 
syrup showed no indications of endosmosis. 
1 reduced the thickness of the plate of marble 
to one millimeter. In this state it lost by fil¬ 
tration, in the space of a day, twenty-one milli¬ 
meters of water measured in the tube. I put 
into the endosmometer, which this plate of 
marble closed, the same syrup which had been 
used in the preceding experiments, and the 
density of which was 1.12, and I now ob¬ 
tained an endosmosis which manifested itself 
by an ascension of seven millimeters in four- 
and-twenty hours. This last experiment proved 
to me that carbonate of lime was not, as I had 
hitherto found it, totally without the power to 
produce endosmosis. I wished to compare 
this plate of marble with a piece of bladder of 
the same surface under the double point of 
view, of their permeability, and their respec¬ 
tive properties of producing endosmosis. Having 
therefore taken off the plate of marble which 
closed the endosmometer, I replaced it by a 
piece of bladder whose permeability to water I 
measured in the same manner as above. I found 
this permeability very nearly equal to that of 
the plate of marble of one millimeter in thick¬ 
ness. I then put into this endosmometer 
some syrup similar in density to that which I 
had used in the same endosmometer closed 
with the plate of marble. The endosmosis 
which I obtained raised the syrup seventy-three 
millimeters in three hours. Thus the permea¬ 
bility to water being equal in the bladder and 
in the plate of marble, the endosmosis pro¬ 
duced by the first was to the endosmosis pro¬ 
duced by the second as 584 is to 7, a most 
extraordinary difference, and difficult to be 
accounted for. These experiments prove that 
carbonate of lime is but very little apt to pro¬ 
duce endosmosis, in which it differs singularly 
from baked clay, thin laminae of which are 
almost as apt to produce endosmosis as organic 
membranes. 
The varieties of sulphate of lime which may 
be employed in endosmometrical experiments 
are not sufficiently numerous or of sufficient 
variety of permeability for it to be possible to 
appreciate the properties of this substance in 
relation to endosmosis. I found that the sul¬ 
phate of lime used in the manufacture of 
plaster in the environs of Paris, employed in 
thin plates to close an endosmometer, did not 
produce endosmosis. But this mineral is per¬ 
haps too easily permeable. In fact it is found 
impossible to obtain endosmosis when the in¬ 
terior fluid of the endosmometer flows easily 
by filtration, in virtue of its weight, through 
porous plates. I should say as much of plates 
of freestone (grés) which I have employed 
without success in these experiments, but that 
I recollect to have obtained the phenomenon 
in a very slight degree with a plate of freestone 
very close-grained and very little permeable to 
fluids. 
I have tried a variety of experiments shew¬ 
ing that an increase of temperature increases 
endosmosis. This result has been confirmed 
by repeated experiments. 
The quantity of the same fluid introduced 
by endosmosis, and with the same sort of per¬ 
meable partition, is generally in proportion to 
the extent of surface of this partition. The 
following experiment demonstrated this fact. 
I took two endosmometers, the membranes of 
which, taken from the same bladder, were of 
diameters in the relation of one to two ; I filled 
the reservoirs of these two endosmometers with 
syrup of equal density, and then plunged them 
into pure water. I had taken care to weigh 
them previously with great exactness. After 
continuing the experiment for two hours, I 
weighed the instruments afresh, and found in 
the large endosmometer four times as great an 
increase of weight as in the small one, which 
proved that the first had introduced, by endos¬ 
mosis, four times as much water as the second. 
This relation was exactly that of the extent of 
surface of their respective membranes, the 
diameters of which were as one is to two, and 
their surfaces consequently as one is to four. 
I have thus enumerated the effects ; let us 
now endeavour to ascertain their causes. 
The first idea which presented itself to my 
mind to explain the phenomenon of endosmosis 
was that it was owing to electricity. We know 
that effects exactly similar to those of endos¬ 
mosis are produced by means of the electricity 
of the voltaic pile in the experiment of M. 
Porret, inserted in the Annules de Chimie, 
vol. xi. p. 137. This naturalist having divided 
a vessel into two compartments by a septum of 
bladder, filled one of the compartments with 
water, and put only a small quantity in the 
other. Having placed the positive pole of the 
pile in communication with the compartment 
full of water, and the negative pole with the 
compartment containing little water, the fluid 
was forced through the bladder from the full 
compartment into the almost empty one, and 
there rose to a higher level than that to which 
it was reduced in the original full compart¬ 
ment. 
I varied this experiment by applying it to my 
own apparatus. I put pure water into an 
endosmometer, the membrane of which was 
plunged into water. I made the interior water 
of the endosmometer communicate with the 
negative pole of the pile, and the exterior
        

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