MITOCHONDRIA IN TISSUE CULTURES 379 



The difference in the results obtained when these dyes are 

 used upon dead cells and when used upon living cells shows 

 clearly that the chemical conditions which exist in the living 

 cell are quite different from those in the dead cell. What hap- 

 pens in the living cell to prevent the mitochondria and fat glob- 

 ules from taking on the pink or blue color which is assumed 

 immediately upon the death of the cell? Was the dye itself 

 oxidized and why did the vacuoles and certain other granules 

 stain? The vacuole certainly does not take the pink color due 

 to the presence of fat of any kind, for death of the cell would 

 hardly remove the fat but would only change it possibly from 

 neutral to acid fat and the vacuole should then change from 

 pink to blue color instead of fading out entirely. If on the other 

 hand the pink color is due to the alkaline nature of the vacuoles, 

 why then does it not either remain pink or else become blue? 

 Why does the nucleus remain unstained until death of the cell 

 begins and then the nucleolus first take on the stain and later 

 the nucleus? Is the pale blue color of the nucleus after brilliant 

 cresyl blue 2 b in the living cell a delicate indicator that the cell 

 is injured by the dye? These are but a few of the questions 

 suggested by the different action of these dyes upon the dead 

 and the living cell and which must be left for the physiological 

 chemist to solve. 



This change is most readily seen when a cell has first been 

 stained while it is living and then fixed under the microscope. 

 As the preparation dies the pink vacuoles fade out and the 

 nucleolus, the nucleus, cytoplasm, fat globules and mitochondria 

 stain. This is not due to the direct action of the fixative upon 

 the stain itself since a fixed preparation which has been well 

 washed with Locke's solution gives the same results with these 

 dyes. 



Iodine 



It might be mentioned in this connection that while the vapor 

 from a crystal of iodine did fix the mitochondria as reddish 

 brown threads, rods and granules, there was no evidence of 

 any port wine colored granules of glycogen attached to any 



