PROTOPLASMIC PERMEABILITY 143 



the globule or internal phase; the more concentrated solution, 

 the continuous or external phase. Such systems are stiff gels. 

 In either case, whether the dilute phase act as medium or as 

 globules, it is obvious that the physical properties of the system 

 will be altered markedlj^ simply by the passage of water from one 

 phase to the other. In other words anything which changes the 

 disfribution of water between the phases will greatly affect the 

 properties of the material. In sols and gels of gelatine and other 

 simple emulsoids this distribution of w^ater is known to be affected 

 by temperature, the presence of salts and other dissolved sub- 

 stances, and even by mechanical stress. All of these things 

 affect the viscosity'' and other physical properties of the colloid, 

 sometimes in large degree. 



It seems not improbable that a sunilar state of affairs exists in 

 protoplasm, that two (at least) of the liquid phases of protoplasm 

 differ importantly only in the proportions of water which they 

 contain, and that the distribution of the water between these two 

 phases may alter without death of the protoplasm. Such changes 

 in the distribution of the water would explain the known facts 

 of permeability more simply than any hypothesis with which 

 I am acquainted. But ability to explain the facts is only part 

 of the duty of an hypothesis. This suggestion is not intended 

 as a "theory" of permeability or as more than a provisional way 

 of viewing the facts; a way which may prove to contain a part 

 of what is probably a very complex truth. 



The comparison of this hypothesis with the facts and with 

 other hypotheses will be facilitated by a picture of the conditions 

 in a protoplasm having the structure which is postulated. Two 

 phases are important; the liquid globules and the liquid medium 

 in which they are suspended. Both are to be imagined as inti- 

 mate mixtures, perhaps solutions, of some colloid-forming sub- 

 stance with water. Doubtless real protoplasm contains several 

 other phases, solid and liquid, and doubtless the mixtures which 

 form the two phases important to this hypothesis are not really 

 simple solutions of a simple substance. For purposes of explana- 

 tion these complexities may be disregarded. Considering the 

 two phases mentioned, it is obvious that the globules of the inter- 



