458 A NOTE ON ADSORPTION [ch. 



Our next and last illustration of the effects of adsorption, which 

 we owe to the work of the late Professor A. B. Macallum* of 

 Montreal, is of great importance ; for it introduces us to phenomena 

 in regard to which we seem to stand on firmer ground than in some 

 of the foregoing cases, albeit the whole story has not been told. 

 In our last chapter we were restricted mainly, though not entirely, 

 to a consideration of figures of equilibrium, such as the sphere, the 

 cyhnder or the unduloid ; and we began at once to find ourselves in 

 difficulties when we were confronted by departures from symmetry, 

 even in such a simple case as the ellipsoidal yeast-cell and the 

 production of its bud. We found the cylindrical cell of Spirogyra, 

 with its plane partitions or its spherical ends, a simple matter to 

 understand; but when this uniform cylinder puts out a lateral 

 outgrowth in the act of conjugation, we have a new and very 

 different system of forces to account for and explain. The analogy 

 of the soap-bubble, or of the simple hquid drop, was apt to lead us 

 to suppose that surface-tension w^as, on the -whole, uniform over 

 the surface of the cell; and that its departures from symmetry of 

 form were due to variations in external resistance. But if we 

 have been inchned to make such an assumption we must now 

 reconsider it, and be prepared to deal with important localised 

 variations in the surface-tension of the cell. For, as a matter of 

 fact, the simple case of a perfectly symmetrical drop, with uniform 

 surface, at which adsorption takes place with similar uniformity, 

 is probably rare in physics, and rarer still (if it exist at all) in the 

 fluid or fluid-containing system which we call in biology a cell. 

 We have more to do with cells whose general heterogeneity of 

 substance leads to quahtative diSerences of surface, and hence 

 to varying distributions of surface-tension. We must accordingly 

 investigate the case of a cell which displays some definite and 

 regular heterogeneity of its liquid surface, just as Amoeba displays 

 a heterogeneity which is complex, irregular and continually 

 fluctuating in amount and distribution. Such heterogeneity as we 

 are speaking of must be essentially chemical, and the preliminary 

 problem is to devise methods of " microchemical " analysis, which 

 shall reveal localised accumulations of particular substances within 



* See his Methoden u. Ergebnisse der Mikrochemie in der biologischen Forschung; 

 Asher-Spiro's Ergebnisse, vn, 1908. 



