164 PHYSIOLOGICAL KEGULATIONS 



of water content is one that gets over the stage of "feeling" its 

 isolation, so that for a time equilibration is complete. At present 

 no such tissue is recognizable. 



§ 66. Isolated cells 



Isolated cells are susceptible of study by the same methods. 

 With due attention to ' ' survival, ' ' freshly isolated blood cells and 

 previously cultured other cells have been subjected to volume 

 changes. But cells rendered visible by direct fragmentation of 

 massive tissues are equally available (Shear and Fogg, '34). Cells 

 already isolated are not considered here ; it is more convenient to 

 classify unicellular s of all sorts, as organisms (§ 51 to § 54) rather 

 than as cells. 



a. Erythrocytes. For the most part, the rates at which these 

 cells change their volumes have been studied by opacitometers. No 

 instances seem to have been reported in which the changes mea- 

 sured represent recoveries toward the volumes characteristic of cells 

 in vivo. One deterrent to obtaining such recovery data is the belief 

 that they can all be predicted from measurements of rates of swell- 

 ing and shrinking in initiatory states ; however, recovery requires 

 specific measurements. Mammalian erythrocytes are believed to 

 exchange other substances than water, whether they be kept in 

 plasma or in other prepared media (Rous and Turner, '16; Davson 

 and Danielli, '38). Diversities among species may be expected. 



b. Leucocytes under certain conditions maintain regular 

 (spherical) shapes, and so their changes of volume may be followed 

 with an opacitometer. The data are limited to swelling in hypo- 

 tonic solutions, followed by shrinking as recovery supervenes (fig. 

 100). While it is possible that the absolute rates reported are 

 limited by other factors than the cells themselves, for the present 

 the exchanges may have been at the rates recorded. Loss of water 

 (recovery) occurs somewhat more quickly than the initiatory 

 change of swelling. 



c. Fibroblasts in plasma cultures have been measured by mi- 

 crometry of single cells (Brues and Masters, '36), but not during 

 recovery toward original volume. It appears that fibroblasts from 

 four sources (chick embryo, rat embryo, mouse sarcoma 180, and 

 rat tumor 256) exhibit nearly equal apparent permeabilities to 

 water upon transfer from 0.15 M to 0.05 M sodium chloride solu- 



