454 Mr. W. Stiles and Dr. F. Kidd. Position of the 



(b) Sodium Chloride {Potato). — The results obtained with potato tissue are 

 complicated by the much greater exosmosis which occurs. Potato is also 

 found to be less tolerant of the experimental conditions than carrot, and it is 

 difficult to avoid injury and death of the discs due to secondary causes 

 incident on the conditions of immersion. The differences between carrot 

 and potato will be dealt with more fully in a subsequent paper, in which 

 attention is centered on the phenomenon of exosmosis into distilled water 

 in the case of various tissues. In the present research it has been found 

 convenient to use carrot tissue mainly, and only a few experiments were con- 

 ducted with potato. 



The results of a series of experiments with sodium chloride are given in 

 Table IV and in fig. 2. "When the results are considered in the same way as 

 those obtained with carrot tissue, that is, taking the initial conductivities as 

 zero in all cases, and the curves representing the exosmosis into distilled 

 water as a base line, the same conclusions appear. The amount of absorp- 

 tion increases with increasing concentrations of salt, and the rate of absorption 

 is relatively slow. 



(c) Copper Svlphctte {Carrot). — -We are here dealing with a highly toxic 

 substance, and the results obtained (Table V and fig. 3) are of a different nature 

 from those just described. The effect of the salt in all concentrations used is 

 to kill the tissue by the end of the experiment. The action of the copper 

 sulphate in all concentrations is greatly to increase the amount and rate of 

 exosmosis from the beginning of the experiment onwards, the rate of 

 exosmosis increasing in parallel with increasing concentrations of copper.* 

 Exosmosis exceeds absorption in all cases. If, as we conclude, the action of 

 the copper is very rapidly to destroy the organisation of the living cells and 

 to render freely diffusible the full amount of contained electrolytes, this 

 result is in accordance with expectation, as the internal concentration of 

 salts in the tissue is equivalent to a conductivity of about 15,000, while the 

 conductivy of the strongest solution of copper sulphate used amounts to only 

 about 3200. The curves in fig. 3 also show that the increasing initial rate of 

 exosmosis with increasing concentrations of copper sulphate is faster than 

 the increasing rate of absorption of the copper sulphate. The final condition 

 reached corresponds to an approximately equal distribution of all electro- 

 lytes (both tissue electrolyte and copper sulphate) throughout the whole 

 system, i.e., bathing liquid and tissue. This type of equilibrium condition is 

 characteristic of dead tissue in contrast to living tissue, and is dealt with 

 more fully in an ensuing section. 



* The type of exosmosis curve obtained in the action of a toxic substance upon tissue 

 is fully dealt with in an earlier paper. See Stiles and Jorgensen (12). 



