Observations on Behaviour of Turgescent Tissue. 67 
According to Osterhout, 1 very dilute solutions produce a reversible 
decrease of permeability to electrolytes in the thallus of Laminaria ; 
and this would probably be correlated with increased resistance to 
the osmosis of water. If the same hold for protoplasm generally 
such a dilute solution should give a curve lower than that for an 
equi-moleculur solution of an inactive substance, such as sucrose 
appears to be, but of similar form ; except that the final total 
expansion might be somewhat greater owing to the protoplasm being 
rendered a more nearly perfect semipermeable membrane. 2 
The M/100 solution (0T2%), the weakest used, should, however, 
on the basis of Osterhout’s results give a different type of curve, 
causing first a reversible decrease, later an irreversible increase of 
permeability ; but there is no sign even in the curve for the M/50 
solution of the exosmosis which would follow in this later stage. A 
repetition is desirable with larger“volumes of solution and every 
precaution against dilution during the course of a prolonged 
experiment. Solutions rather stronger, which produce at once (as 
far as Osterhout could observe) an increase of permeability, should 
give a curve showing at first a diminished rate of entry of water, due 
however to exosmosis of solutes, not to decreased permeability to 
water—the same form of curve, in fact, as is obtained with mercuric 
cyanide. 
With the latter, the results are explicable on the basis of an 
increase of permeability and consequent exosmosis of solutes which 
vary in degree and rate with the strength of the solution. The more 
rapid fall after the first five hours in the M/100 and M/50 than in 
the M/10 may be due to the larger volume of solution that had 
entered and therefore a probably deeper penetration. The M/100 
solution of mercuric chloride contrasts similarly with the other 
strengths of that salt and the same explanation may hold. 
Mercuric chloride precipitates the proteins of the membrane, 
and quickly makes exosmosis possible, though this is far less rapid 
than with chloroform, perhaps partly because of a more general 
permeation of the tissue by the latter. 3 Although chloroform is 
very soluble in lipoids, it would be less firmly held than is mercuric 
1 Science, 37, 1913, p. 111. 
* On the effect of permeability on the isotonic coefficient and the maximum 
degree of turgor, compare Lepeschkin, 1909, Ber. d. d. Bot. Ges. XXVI a, p. 198, 
and XXVII, p. 129. 
3 Chloroform vapour may diffuse to the interior by way of the air spaces. 
