28 



THE CELL AND PROTOPLASM 



should fall to zero. Apparently such a 

 change from a low positive value to zero 

 does occur. 



If the injected oil drop has been in con- 

 tact with' the cytoplasm for a protracted 

 period, induced cytolysis will have no ef- 

 fect. Neither is it possible to obtain the 

 crinkling" effect when the oil drops are in- 

 troduced into the cytolj'tic debris later than 

 a few minutes after cytolysis has occurred. 



Since the Devaux crinkling effect of the 

 oil drop with the oil-retraction method is 

 not noticeable in the living cytoplasm, it is 

 concluded that the proteins in the living 

 cell do not accumulate on experimentally 

 introduced surfaces while the protoplasm is 

 intact. This suggests that the proteins are 

 not freely diffusible and adsorbable in pro- 

 toplasm, and that, therefore, these proteins 

 may be bound together to form some kind 

 of continuous phase. 



The fact that spontaneous crinkling oc- 

 curs only when the oil is introduced almost 

 at the instant of cytolysis and not later 

 suggests that the protoplasmic proteins in- 

 itially break down into unstable, high- 

 molecular-weight complexes which, as they 

 are adsorbed, break further into low-mo- 

 lecular-weight derivatives. These molecules 

 spread at the interface to produce the 

 crinkling effect. 



The high-molecular-weight complexes pro- 

 duced at the onset of cytolysis must be 

 unstable and have a short life, since heavy 

 protein molecules are rarely isolated from 

 protoplasm. Introduction of an oil surface 

 into protoplasm just prior to cytolysis 

 makes possible their adsorption at the mo- 

 ment of cytoh'sis and before further dis- 

 sociation occurs. It is known that high- 

 molecular-weight proteins will not spread 

 until dissociation to units of low molecular 

 weight is completed. From these facts we 

 may infer the following about the cytolys- 

 ing protoplasmic proteins at oil surfaces: 

 first, their adsorption, r()lh)wed by dissocia- 

 tion into smaller units; and tlien, a globular 

 to a lamiiuir transformation. Spontaneous 

 increase of interfacial area follows such 

 change in configuration of the protein 

 molecules. 



We therefore have two factors which in- 

 duce the spontaneous crinkling effect: (a) 

 the adsorption of sufficient protein to cause 

 the entire interface to be covered ■with at 

 least a monolayer, and (&) a conversion of 

 a globular to a laminar configuration of the 

 protein molecule, promoted by the tension 

 and other characteristics of the interface. 



There is other experimental evidence for 

 a peculiar state of the proteins in living 

 cells. One is from the injection into proto- 

 plasm of solutions of colorimetric indicators 

 for measuring intra-cellular pH. The large 

 variety of indicators used, including the 

 sulphone-phthalein indicators, give consis- 

 tent results irrespective of their chemical 

 constitution, and there seems to be no pro- 

 tein error such as occurs in solutions of 

 non-living proteins. A striking example 

 is bromthymol blue, which gives an incon- 

 sistent color with ordinary protein solutions 

 when compared with phenol red ; the color 

 it gives when injected into a living cell 

 agrees with the color virage presented by 

 both brom cresol purple and phenol red. 



Moreover, the acid of injury which has 

 always been found to be associated with 

 cytolysis may be explained on the basis of 

 an irreversible dissociation of protein 

 macromolecules to low molecular weight 

 proteins, which releases increased numbers 

 of ionizable carboxyl groups. 



Finally, there is the work of Vies and Gex 

 (1934) on the ultra-violet absorption spec- 

 trum of sea-urchin eggs. They detected 

 different absorption curves in the living 

 cells from those of cytolyzed cells; the lat- 

 ter had absorption curves resembling iso- 

 lated albumin. 



One of the most striking characteristics 

 of protoplasm is that mechanical crushing 

 destroys it. 'This holds not only for the 

 integrated cell but also for any viable frag- 

 ment of protoplasm which may be spon- 

 taneously or experimentally separated from 

 the cell. The implication has long been 

 recognized by cytologists that the property 

 of life depends ui)ou a definite architecture 

 of structural nature. Verworn and E. B. 

 Wilson have defined protoplasm as a mor- 

 phological concept. Hypothetical units of 



