456 Scientific Intelligence. 
ing but the cuticular layers. It was these colloid membranes which 
served to repeat Graham’s experiment. Except in a few modifica- 
tions of detail, he followed strictly the course of that illustrious 
physicist. 
First, to ascertain by the dialysis of air alone that the membrane 
is intact, presenting no rents, three experiments were made on the 
16th, 17th and 18th of March. They gave the following results at 
the end of six hours :— 
16th. Yith. sth. 
Vol. of gas collected, 5°2cm % 5°5cm # 7-0 em$ 
Vol. of O absorbed by 9 a3 « a9 «& 
pyrogallate of potash, 
Proportion of oxygen, 30° 41% 1% 
tl itions of externa 
cially of moisture, the conclusion may be drawn that oxygen passes 
1 
In four experiments made with different membranes, he obtained 
the following results :— 
ist. 2d. 3d. 4th. 
CO? 1 1 1» s 
N 155 13" 40™ 152 30™ 14° 
O 6» h 99m yh 5h 40™ 
The experiments made under conditions of pressure, tempera- 
ture, and moisture, which doubtless were not identical, yet agree 
sufficiently well with those of Graham, and allow us to conclude 
that the natural colloid surfaces of vegetables have for carbonic 
acid an admissive power which is thirteen to fifteen times as great 
as that of nitrogen, and six or seven times that of oxygen. : 
Some days after he repeated the experiment with carbonic acid, 
perfectly dry, and found for its velocity compared with nitrogen 
numbers varying from nine to eleven; it seems then that dry car- 
bonic acid passes less rapidly than when moist. i 
Replacing the vegetable film by caoutchouc, he obtained a sim- 
Uar result, The difference in the case of dry oxygen and nitrogen 
Is less marked. , 
#te remarks, in conclusion, that these experiments prove the di- 
alysis of carbonic acid through the cuticle of leaves, just as much 
as those of Dutrochet on membranes and aqueous solutions prove 
endosmose by cellules, or the experiments on absorption made 
