GuillJermond - Atkinson — 144 — Cytoplasm 



ondly, the lower limit for accumulation of Nile blue placed at a pB. 

 value below 3 (2.4). 



These apparent irregularities are easily interpreted. In study- 

 ing the accumulation of neutral red by yeast, it is noticed that the 

 quantity of dye retained by the cells varies incessantly, because of 

 the alternate excretion and accumulation of the dye. There is not 

 at any time, therefore, a true equilibrium and hence no real sig- 

 nificance can be attributed to the absorption curve of neutral red in 

 terms of pH values. 



To obtain satisfactory results, a 1% solution of KH2PO4 must 

 be used. In it the yeast does not grow and does not excrete the 

 dye. Under these conditions, the amount of dye absorbed by the 

 yeast varies very little and a state of equilibrium is reached which 

 makes it possible to study accurately the accumulation of neutral 

 red in terms of pH. The curve obtained in this medium is similar 

 to that for cresyl blue. It begins at pB. 5.6, rises steadily to pB. 9 

 and then flattens out. 



With regard to the second point, namely, the behavior for Nile 

 blue, it must be taken into account that this dye is absorbed by the 

 protoplasm of yeast and if the other dyes (neutral red and cresyl 

 blue) have their lower limit of accumulation set at pB 5.6, one 

 may think that the isoelectric point of their cytoplasmic colloids 

 must be situated a little below this pB and that there occurs in its 

 neighborhood a tightening of the micelles which prevents the 

 penetration of these dyes, for they have not, like Nile blue, an 

 affinity for the cytoplasm. 



Our experiments showed, in addition, that the phenomenon of 

 the accumulation of vital dyes in the vacuoles seems, up to a certain 

 point, to follow the law of Freundlich and to correspond to an 

 adsorption^ 



The net result of these facts is that vital dyes, although not 

 having any injurious effects on cells when used in weak doses, do 

 behave as toxic substances and are always excreted into the vacu- 

 oles, where they remain (phanerogams), or from which they may 

 be excreted into the exterior medium. The facts show us at the 

 same time that the vacuoles are the centers of accumulation for 

 toxic substances collected in the cells. These facts show that cer- 

 tain dyes may be taken up by the cytoplasm but that this is always 

 transitory and the dye is very shortly excreted into the vacuole. It 

 is only when the dye has been localized in the vacuole that the cell 

 can grow and divide. There is an important difference, however, 

 between the behavior in the phanerogams and in the fungi (Sapro- 

 legnia excepted). Whereas the phanerogam cells can grow when 

 the dye has accumulated in the vacuole, those of the fungi can not 

 and excrete the dye accumulated in the vacuole into the external 

 medium. Once rid of the dye, the fungal cells begin to grow. 

 Nevertheless our recent research (Guilliermond and Gautheret) 



1 



^Translator's vote. A fuller discussion of the entire subject is to be found in an article by 

 Guilliermond, received after this volume went to press: La Coloration vitale d'apres des 

 Travaux recents (Montpellier Medical 1940, No. 1:1-24). 



