222 PROTOPLASM 



incompatible with life, but this appears to be true only when it is 

 irreversible (if we may speak of reversible coagulation). 



The effect of anesthetics on protoplasmic consistency has been 

 extensively investigated. Lloyd finds that the application of low 

 nonlethal concentrations of narcotics (ethyl alcohol, ether, chloro- 

 form) is accompanied by reduced viscosity (of Spirogyra), while 

 higher concentrations increase the viscosity presumably by 

 dehydration. Other workers find a pronounced increase in 

 protoplasmic viscosity when narcotics are added. 



Electricity produces an increase in protoplasmic consistency; 

 the change, if not carried far, is reversible. Klihne, as early as 

 1864, used electrical stimulation as a procedure for the study of 

 reversible viscosity changes in protoplasm. The interesting 

 experiment of Bayliss on the gelating effect of a mild electric 

 shock on Amoeba has been referred to (page 215). 



Mechanical irritation may cause a change in consistency; it 

 may bring about a complete collapse in the intricate structure 

 of a dividing cell. An egg in mid-mitosis may, on puncture with 

 a needle, completely collapse, leaving no vestige of the former 

 asters and spindle. Such behavior is closely analogous to the 

 thixotropic collapse of an iron oxide gel (page 150). 



Death brings on marked changes in the viscosity of protoplasm. 

 The usual change which accompanies death is coagulation, 

 though often replaced or followed by complete disintegration. 



Application to Physiology. — The importance of studies on the 

 viscosity of protoplasm is indicated by the remarkably wide 

 application of them to physiology. There is a correlation 

 between the viscosity and the permeability of the plasma 

 membrane. The formation, control, and repair of the proto- 

 plasmic membrane — indeed, all surface phenomena in the cell, 

 such as the distribution of protein and fat substances — are to a 

 great extent controlled by the viscosity of protoplasm. Amoe- 

 boid movement has long been regarded as related to, if not 

 determined by, changes in viscosity. Viscosity changes have an 

 important bearing on the dynamics of mitosis. 



The mechanism of the operation of contractile vacuoles has 

 to do with variations in consistency, as Taylor and Lloyd have 

 shown. Gasser and Hill have discussed the role of viscosity in 

 the dynamics of muscular contraction. Probably all forms of 

 tissue contractility are associated with viscosity changes. 



