1917] BROOKS—PERMEABILITY 313 
ience may be considered as the amount of salt passing through the 
tissue, expressed as the percentage of the amount passing through 
tissue bathed by sea water, as shown in the ratio column of table II. 
If the protoplasm be assumed to be wholly impermeable to salts 
of lanthanum, the figure 0.45, expressing the permeability of the 
tissue as a whole, would in this case represent diffusion through 
the intercellular substance only. Since this part of the tissue has 
been shown (cf. table I) to have no appreciable selective permeabil- 
ity, we may assume that not more than 0.45 of the permeability 
of the tissues to sea water, which is 1.07, is due to passage of salts 
TABLE II 
PERMEABILITY OF LIVING Laminaria 
First PERIOD SECOND PERIOD Ratio 
F) 2 3 
Be U 3 Dura me Dura wees ae 
5] - ~ poy 
PE seltica pc-aerdl ond ee 58 Upper solution|Lower solution “ago eg 3 Z z Z 
gm aeae geak! Sia 
butt OF i & 
18..| Half se. a. 2:05 | 0.73 | Half sea Sea water | 2:00 | 0.78 | 1.07 
water water water 
19.. oi i 2:00 | 0.79 | NaCl, NaCl, 2:00 | 1.1m | 1.41 
°0.26M °o.52M 
22.. . x 2:06 | 0:73 | CaCl, CaCl,, 2:02 | 0.51 | 0.70 
0.14 0.28 M 
17a. « “ 1:35 | 0.73 | Las(NO,)s, | Las(NO,)s, | 1:35 | 0.33 | 0.45 
0.05 M ‘o.10M 
through the intercellular substance. There remains 1.07—0.45= 
©.62, which represents that part of the salt which passes through 
the protoplasm. In sea water, therefore, a minimum of on or 
58 per cent of the salt, passes through the protoplasm, but the 
exact significance of this figure is doubtful owing to the arrangement 
of the protoplasmic masses in the tissue. 
In order to show the order of magnitude of the total diffusion 
through the living tissue, the results may be expressed in terms 
of the amount of salt in gm. molecules passing through 1 sq. cm. of 
tissue per hour. Ignoring the exceedingly slight change in molec- 
ular conductivity induced by such small changes of concentration, 
