Stiles and J 0rgensen. — Studies in Permeability . V. 417 
From the data so obtained curves are constructed, showing the relation 
between time and the absorption by, or exosmosis from, the tissues under 
different conditions. 
The Variability of the Tissue used and the 
Probable Error of Experiment. 
Although it might be expected that potato and carrot would yield 
very uniform tissue, so that individual variations would be largely eliminated 
in experiments with 20 grm. of tissue (40 discs), yet actual measurements 
show this is far from being the case. The variability of such tissue in 
regard to water absorption and excretion is indeed surprisingly large. 
Probably the previous history of the tissue is in a great measure responsible 
for this variability, although inherent differences may possibly play a part. 
In the experiments with potato the same variety was used throughout so 
that inherited differences should be reduced to a minimum. It is a matter 
of common knowledge that organs such as potato and carrot gradually 
lose water during storage, and evidently different degrees of desiccation of 
different samples will give rise to notable differences in regard to absorption 
or exudation of water. 
In Table I are shown the amounts of water absorbed by nine separate 
lots of potato discs cut at the same time and subjected to the same experi- 
mental conditions. In these experiments, as they were cut, the discs were 
dried between blotting-paper and weighed out into lots of 20 grm. It will 
be observed how wide are the variations between individual samples, and 
that these are indeed due to differences in the tissue itself is indicated by 
the fact that the differences are maintained throughout the experiment. 
Table I. 
Water absorbed by 20 grm. of Potato from Distilled Water . 
Sample . 
Gain in 
Weight of 20 
grm . of Potato < 
after various times . 
o-8 hr . 
3-8 hrs . 
18-15 hrs . 
47*3 hrs . 
70-8 hrs . 
grm. 
grm. 
grm. 
grm. 
grm. 
1 
0-52 
1 -o8 
2*20 
2-77 
3 * 04 . 
2 
o*53 
i*37 
2-49 
3*05 
3-22 
3 
°*59 
i-43 
2-63 
3‘3i 
3-60 
4 
0-36 
i-o8 
2-31 
2»6o 
3*40 
5 
0*70 
i -49 
2-93 
3.66 
4-12 
6 
o*6 1 
1-63 
2 * 6.3 
3.28 
3*6o 
7 
0-56 
1-36 
2*33 . 
2*70 
3*24 
8 
0-50 
T *39 
2*33 
3.00 
3-67 
9 
o*57 
i*53 
2*47 
3 -I 7 
3*57 
Mean 
o*55 
i'37 
2*48 
3*05 
3-5o 
Pm 
+ 0*02 
±0-04 
±0*07 
±0-075 
±0-07 
It is possible to form an idea of the degree of accuracy of the mean 
values by calculating their probable error. From Table I it will be observed 
