FILTRATION. 
283 
On tin.' other band, the older experiments of Schmidt 3 with gum 
and albumin gave quite <>]']" .si t <• results; thus (p. 364 of L863 paper) — 
Albumin through Ox Pericardium. 
Concentration of Original „ 
Solution per Cent. Pressure. 
Pi r • 'iit. Albumin in Filtrate. 
Per Cent. Albumin in Original 
Solution. 
1-6 
| 220 mm. 
[ 120 mm. 
•7037 
•6638 
1 220 mm. 
3-5 
| 120 mm. 
•7050 
•7712 
And the experiments of Gottwalt 2 and v. Regeczy 3 are in agreement 
with those of Schmidt. 
According to Lbwy, 4 who filtered serum and egg albumin solutions 
through pig's bladder at constant pressure, rise of temperature affects 
the quantity of the organic solids filtering more than the inorganic, and 
such slight temperature changes as from 37°'5 to 41° - 5 0. have a distinct 
effect. 
It is therefore evident that our knowledge of the phenomena of filtra- 
tion through animal membranes is at present very restricted, and it is 
of course impossible to directly apply the results of the above observers 
to nitrations in the living body. No experiments, perhaps, have more 
clearly pointed out tli" difference between a dead and living filter than 
those of Tigerstedt and Santesson" with the frog's lung. A fresh frog's 
lung, filled with 6 per cent, sodic chloride solution, will stand a pressure 
of some 13 or 14 mm. of mercury without filtering for many hours ; 
heating in water at -~4 I !., or treatment with weak acetic acid, frog's bile, 
weak sodic hydrate, or distilled water, at once, however (presumably by 
killing the cells), allows filtration. Leber, 6 moreover, showed that the 
fresh cornea, provided the epithelium- of the membrane of Uescemet is 
intact, will stand a pressure of 200 mm. of mercury, but at once 
allows filtration to occur when the epithelium is removed, the tissue 
of the cornea itself allowing fluid to pass. 
It must be confessed that experiments on living membranes (and 
these alone) can give any information of real value ; and, furthermore, it 
must be remembered that filtrations in the body are, as a rule, accom- 
panied by osmotic phenomena, since filtration must nearly always occur 
from one solution into another, and not into air, as in most experiments. 
In concluding this article, a word must be said with regard to the 
theory that in some cases the cells of a part take some active part in 
moving solutions across membranes. So little is known of cell mechanics, 
that if such a process does take place we have certainly no conception 
of its modus operandi, and it is at least probable that a process con- 
sidered to-day as a ''vital action'' may in the future • become capable 
of a simpler explanation. Certainly, if the same solution is placed on 
1 Loc. cit. 
6 Arch. f. Ophth. 
2 Loc. cit. 
Leipzig, 187' 
3 Loc. cit. 4 Loc. cit. 
Bd. xix. Abth. 2, S. Vi:<. 
5 Loc. cit. 
