22 



THE CELL AND PROTOPLASM 



been possible in some cases to induce the 

 reverse change, i.e., from the sol to the gel 

 (Chambers 1938a). Fragments of proto- 

 plasm which are pinched off from an unfer- 

 tilized sea-urchin egg may act, at one mo- 

 ment, as if solid, maintaining deformed 

 shapes; while at another moment, they act 

 as if liquid, rounding up into spheres. 

 Hence, to speak of protoplasm as a liquid 

 or as a solid has little meaning. 



The relation of the nucleus to the cyto- 

 plasm of the cell has always claimed the 

 attention of cytologists. Experimental evi- 

 dence has indicated that the nucleus is es- 

 sential not only genetically but also for the 

 continued existence of the cell. In certain 

 ciliates the control of these two functions, 

 the so-called kinetic and trophic, has been 

 ascribed to the micro- and macro-nuclei, 

 respectively. Taylor and Farber (1924) 

 showed that the micro-nucleus alone may 

 bear both functions. By means of a micro- 

 pipette they removed the micro-nucleus of 

 over seventy individual Eiiplotes and found 

 this operation was lethal. The importance 

 of the nucleus has also been shown by noting 

 the effect of puncturing one of the nuclei of 

 a binucleated fibroblast in tissue culture 

 (Chambers and Fell 1931). The injury 

 irreversibly coagulated the nucleus and 

 spread into the cytoplasm, producing a 

 granular precipitate and a disruption of the 

 mitochondria in the vicinity. In mono- 

 nucleated fibroblasts puncture of the 

 nucleus resulted in complete disintegration 

 of the cell. On the other hand, in the case 

 of the binucleated cell, the disintegrative 

 changes were temporary and occurred only 

 in the vicinity of the injured nucleus. Com- 

 plete recovery soon followed, evidently be- 

 cause of the presence of the other nucleus. 



The micro-injection technique has af- 

 forded a most fertile field for investigation. 

 A difficulty, which at present has been only 

 partially overcome, is to gauge the precise 

 quantity injected. The amount of solution 

 drawn into a pipette for subsequent injec- 

 tion can rarely be injected completely into 

 the cell. Moreover, except for relatively 

 large cells it is difficult to judge whether 

 the attempted injection of the aqueous solu- 

 tion is successful. A positive reaction is 



generally the only criterion for a successful 

 injection. It is necessary to inject sub- 

 stances gradually, for even minute amounts 

 may result in cytolysis when suddenly in- 

 troduced. On the other hand, the proto- 

 plasm of many cells permits the gradual 

 introduction of surprisingly large amounts, 

 even of water, without destruction. 



It is not possible to deal in detail with 

 the results of micro-injecting indicators 

 which are used for colorimetric determina- 

 tions of the reducing intensity and the 

 hydrogen-ion concentration of protoplasm. 

 Cohen and Chen (1933), using indicators 

 not available in the earlier injection experi- 

 ments on the reducing intensity of various 

 cells under anoxybiosis, have stated that 

 the value for Amoeba duhia is in the neigh- 

 borhood of - 0.260 and - 0.289 volts at pH 

 7.0. They drew this conclusion from their 

 observations that dimethylphenosafranine 

 and safranine T (whose reduction poten- 

 tials are - 0.260 and - 0.289 v. respectively) 

 are only partly reduced in the cell, while 

 sulfonated rosindone with a potential of 

 - 0.380 is not. 



The fact that there was even a partial 

 reduction of the two first mentioned indi- 

 cators is significant because basic dyes tend 

 to be strongly adsorbed. This not only in- 

 creases the capacity factor a great deal, but 

 probably renders the indicator less soluble 

 and, hence, less available for reduction. 

 On the other hand, acid dyes at the pH of 

 protoplasm tend to be very diffusible and 

 more susceptible to the reducing intensity 

 of the protoplasmic system. Hence the 

 non-reducibility of sulfonated rosindone is 

 also significant. Evidently the reducing 

 intensity of protoplasm of the amoeba 

 under nitrogen, (approx. -0.275 v.) lies 

 roughly midway between the potential of 

 the hydrogen electrode {viz., -0.421 v.) 

 and the aerobic reducing intensity of the 

 cell, which has been found to be centered at 

 about - 0.07 V. 



"With regard to the protoplasmic pH, the 

 variable values reported by many investi- 

 gators may be explained, at least in part, 

 by the extraordinary ability of many cells 

 to segregate introduced materials into vacu- 

 oles where the color of the indicator tends 



