May 26, 1916] 



SCIENCE 



755 



of the mice rapidly increased when citrate was 

 admixed with CaCL, or when CaOl. was ad- 

 mixed with citrate, until finally, when the 

 solutions were employed in the ratios of one 

 equivalent of CaCh to two of Na citrate, a 

 destructive effect on the mice could only be 

 observed when, by greatly increasing the con- 

 centration, the dose employed was raised to 40 

 or 50 times that used at either end of the scale. 

 In the process of blood coagulation, all the 

 plasma tubes employed were coagulated 

 rapidly when CaCl, was present in excess of 

 the ratio of 1:2, while no coagulation took 

 place in those tubes in which the proportion 

 of CaCl„ was below this figure. From the re- 

 markable similarity exhibited in these three 

 systems, one purely physical, one purely bio- 

 logical, and one semi-physical and semi-bio- 

 logical, it may well be concluded that the 

 equilibrium of both physical and biological 

 systems of the type described depends upon the 

 maintenance of the colloidal equilibrium of 

 surface films, and that balanced solutions are 

 those in which the proportions of cations or 

 anions adsorbed on or reacting with the col- 

 loidal constituents of the film are compensa- 

 tory, and consequently no change occurs in the 

 equilibrium of the system. 



These drop systems are peculiarly sensitive 

 to changes in physical conditions and to slight 

 variations, such, for example, as an increase or 

 decrease in the proportion of fatty acid pres- 

 ent in the olive oil employed. These varia- 

 tions are of peculiar interest as offering a pos- 

 sible explanation for the variations in perme- 

 ability to food stuffs of actively growing cells, 

 conditioned not only by variations in the pro- 

 portions of electrolytes and of metabolic prod- 

 ucts in their environment, but also by slight 

 variations in the proportions, for example, of 

 lipase or any agent capable of splitting fats or 

 lipoids. In fact these systems are as delicate, 

 or even more delicate than living cells, and 

 are equally difficult to work with. Accurate 

 comparative data can only be obtained by the 

 most scrupulous observance of every possible 

 precaution to insure comparable working con- 

 ditions, and by taking the average of a very 

 large number of experiments. It is interest- 



ing to note in this regard that in such a series 

 of experiments the great majority will lie 

 within a close range of the average, while in 

 certain individual experiments, as in the case 

 of certain individual organisms, extraordi- 

 nary abnormalities may be exhibited. It is 

 not possible in this brief preliminary com- 

 munication to explain fully the mechanism of 

 the drop system, but it may be stated briefly 

 that those forces which promote an increase 

 in the number of drops are always comparable 

 with those which promote the formation of 

 emulsions of oil in water or a system more 

 permeable to water, while those which exert 

 the reverse effect causing a diminution in the 

 number of drops are those which promote the 

 formation of emulsions of water in oil or a 

 system relatively less permeable to water. 

 This is due presumably to the influence ex- 

 erted by various reacting or adsorbed anions 

 or cations on the relative dispersion of the 

 constituents of the film in water, on the one 

 hand, and oil, on the other, thus changing the 

 relative surface tension on the two sides of 

 the film, and promoting the formation accord- 

 ing to circumstances of a system in which the 

 permeability to water and water-borne sub- 

 stances is increased or diminished. 



To turn now to the question as to how this 

 bears on the problem of protoplasmic struc- 

 ture: it is probable that not only soap films, 

 but all concentration films formed at the in- 

 terface between two non-miscible phases, tend 

 to be more or less similarly influenced by ad- 

 sorbed substances. It is not proposed at this 

 stage to consider the case in which the effects 

 produced are simply due to an electric charge 

 conveyed by adsorbed cations or anions, a sub- 

 ject which will be dealt with in a subsequent 

 communication, but simply those cases in 

 which definite soap films are formed and play 

 a role in conditioning the equilibrium of the 

 system. We know that fats and lipoids play 

 an important role in the protoplasmic film. 

 We know that soaps are present in the proto- 

 plasmic system, and, since the soaps in ques- 

 tion will tend to concentrate, as has been seen 

 above, at the interface between the particles of 

 fatty or lipoid material and water, it is quite 



