INJURY AND RECOVERY 97 



investigated by the writer, such as the green alga, Ulva 

 (sea lettuce), the red alga, Rhodymenia (dulse), and the 

 flowering plant, Zostera, (eel grass). It seems to be also 

 true of frog skin as far as the experiments of the writer 

 have gone,''^ In physiological literature it seems to be 

 generally assumed that when recovery occurs at all it 

 is practically complete, as though it obeyed an "all or 

 none" law.^^ It is evident that partial recovery might 



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Fia. 40. — Curves showing rate of respiration of Laminaria agardhii (expressed as per cent, 

 of the normal). The normal rate represents a change from pH 7.78 to 7. 36 in from l^ 

 minutes to 2 minutes, depending upon the amount of material used. The solid lines show 

 rate of respiration while tissue was exposed to hypertonic sea water (sp. gr. 1,130, A**=* — 9.37° 

 approximately). The dotted lines snow stages of recovery after the tissue was put back in 

 normal sea water. Each curve represents a typical experiment. The figure attached to 

 each recovery curve denotes the time (in minutes) of exposure to the solution of hypertonic 

 sea water; thus the uppermost curve represents recovery after an exposure of 5 minutes. 



"^ The recovery experiments on frog skin were few in number and dealt 

 chiefly with the effects of anaesthetics. 



"There are indications in the literature that partial recovery occurs. 

 Thus Leo Loeb and his collaborators Loeb, L. (1903) 1905; Corson-White, 

 E. P. and Loeb, L. (1910) ; Fleischer, M. S., Corson- White, E. P., and Loeb, 

 L. (1912) ; Ishii, C, and Loeb, L. (1914) observed that destruction of the 

 corpora lutea produces a permanently depressing effect on the ovary and 

 that the virulence of tumor tissue is permanently diminished by exposure 

 to heat or certain reagents. In both cases a condition is produced which 

 is intermediate between death and normal vigor. The diminution of the 

 virulence of bacteria by various means cannot be cited as an Illustration 

 unless it is certain that it is not due to the selection of less viru- 

 lent individuals. 



