666 STUDIES ON RESPIRATION. XVH 



It is therefore evident that in all these experiments recovery may 

 be incomplete and even where the tissue is kept for days under the 

 most favorable circumstances there is no tendency in these cases for 

 the recovery to complete itself. This offers a striking parallel to the 

 experiments recently described by Osterhout^ in which all degrees of 

 recovery (depending upon the length of exposure) were observed 

 when Laminaria was placed for a time in 0.52 m sodium chloride (and 

 in other solutions)'* and then replaced in sea water. In this case 

 electrical conductivity was used as a criterion of recovery. 



Fig. 3. Curves showing rate of respiration of Laminaria (expressed as per cent 

 of the normal). The normal rate represents a change from pH 7.78 to 7.36 in 

 from 1^ to 2 minutes, depending upon the amount of material used. The solid 

 lines show rate of respiration during one hour of exposure to isotonic sodium 

 chloride (0.52m for Woods Hole sea water). The dotted lines show stages of 

 recovery after the tissue was put back in normal sea water. Each curve repre- 

 sents a tj^iical experiment. 



It is possible that when recovery is incomplete none of the cells 

 are killed but that their respiration is permanently decreased. It is 

 also possible that some cells continue to respire normally while others 

 are killed and that it is the death of these cells which prevents complete 

 recovery. This question must remain for future investigation. 



3 Osterhout, W. J. V., /. Gen. Physiol., 1920, iii, 15. 



* UnpubHshed experiments by Osterhout on the electrical conductivity of 

 Laminaria show incomplete recovery after exposure to hypo- and hypertonic 

 solutions. 



