Guilliermond - Atkinson — 138 — Cytoplasm 



It would seem today, in the light of investigations of BUNGEN- 

 BERG DE Jong, that the precipitation observed in vacuoles under the 

 influence of vital dyes may perhaps be explained, in many cases, 

 not by flocculation, but by the production of coacervates in the 

 vacuolar sap. According to this idea, there is a formation of a 

 complex between the positive dye and the negative vacuolar col- 

 loid. The colloid may then flocculate as in the yeasts, or else, if the 

 micelles are strongly bound to the dispersion medium, there is a 

 separation of a coacervate phase in the vacuolar sap which, how- 

 ever, still contains dispersed colloidal micelles, as the diffuse color 

 taken by the vacuolar sap indicates. If the dye continues to pene- 

 trate the vacuole, at first the coacervate phase becomes greater and 

 greater. Then the micelles of the coacervate take the charge of 

 the dye and, their repulsion becoming greater than their force of 

 coherence, the coacervate disappears and the vacuole becomes uni- 

 formly stained. An observation which would seem to support this 

 opinion further, is that the precipitates formed under the action 

 of the dye, seem often to be in liquid droplets, capable of changing 



shape and even of becoming vacuolized. 



^r«^^^^^^^^g5>^ Moreover, it seems that all intermediary 



r^^lP^'^^^^^fcih^^ stages in the action of vital dyes between 



m^^^^^^m/^^^'- -m coacervation and flocculation can be 



^^^^^^^^^^^^^^f Another point very clear from our 



^^^ 1^!' ^'iiy'illlf llM l*^ investigations is that staining of the 



^^^r—s^J**^ vacuoles by neutral red is essentially a 



Fig. 88. — Petri dish designed vital phenomenon. As a matter of fact, 



ing material! '" °^^^'''"'*'°" °^ '"" although ncutral red is only slightly 



toxic, if used in too strong concentra- 

 tions, it may cause the death of the cell. This is preceded by an 

 increase in the refractivity of the c>i:oplasm. Then suddenly the 

 vacuole becomes colorless, whereas the entire protoplasm takes on a 

 dark red color. 



There is no formation of vacuoles or artificial granules pre- 

 ceding death in any of the cells which we have observed, and death is 

 always accompanied by destaining of the vacuole. Staining of the 

 vacuole is possible, therefore, only when the cell is living and this is 

 a general fact which applies to the staining action of all vital dyes. 



This fact may be even more satisfactorily observed in the lower 

 algae, for instance in the Euglenas, which are endowed with move- 

 ment. The cells of these algae accumulate neutral red in their 

 vacuoles as long as they are moving but once their movements 

 cease and the cells die, the vacuoles destain and the dye colors the 

 cytoplasm and nucleus. The conclusion to be drawn is that the 

 staining of the vacuoles in a cell constitutes one of the best means 

 of determining if it is alive. Vital staining of the vacuoles and 

 that of the chondriosomes and leucoplasts are therefore clearly 

 differentiated. Vital staining of the last two is possible but when 

 it occurs it is transitory. Usually it is sublethal and does not dis- 

 appear when the cells die. 



