INJURY AND BECOVERY 95 



esis would in no way invalidate the conception developed 

 above, that an individual cell may lose part of its 

 resistance and subsequently regain it, either partially or 

 completely. But there are serious objections to this 

 hypothesis. The appearance of the cells under the micro- 

 scope indicates that they all die at about the same time. 

 Moreover, Inman (1921, B) has recently obtained striking 

 experimental evidence that recovery may be far from 

 complete when practically all the cells are alive. In his 

 experiments he employed a unicellular alga, Chlorella, 

 which does not stain readily with methylene blue as long 

 as it is alive, but stains intensely as soon as it dies. Cells 

 were treated with hypertonic salt solutions until the rate 

 of respiration was greatly diminished. When they were 

 replaced in the normal culture medium, the respiration 

 did not return to normal, but the rate appeared to be 

 permanently lowered. In order to determine whether 

 this was due to the death of a part of the cells they were 

 carefully stained with methylene blue. The percentage of 

 dead cells 20 was practically the same as in the normal 

 culture before treatment with the salt solution. In other 

 words, the incompleteness of the recovery seems to be due 

 to the fact that the metabolism of each cell is permanently 

 lowered. Similar results were obtained when the cells 

 were treated with chloroform; in this case a great 

 depression of respiration was not followed by recovery, 

 but by a greatly lowered metabolism which was perman- 

 ent and which was not due to the death of a part of 

 the cells. 



Some recent experiments of Inman (1921, A) indicate 

 that we obtain similar results whether we use electrical 

 resistance or respiration as the criterion of partial recov- 

 ery. He found that in NaCl 0.52 M the rate of production 



JO 



Tlie cells were counted with a hsemocytometer. 



