288 
R. A. HARPER 
Przibram's figures and ideas are perhaps not as crude as those of Grew, 
but the general consensus of biological opinion is, undoubtedly, that no 
progress has been made along these lines. Such viewpoints lead simply 
into a hopeless cul de sac and seem to make mockery of the whole attempt 
at a chemical explanation of life phenomena. 
The change that came with the recognition of the colloidal condition 
as a phase of material existence comparable in significance to the crystalline 
condition, the solution condition, the gaseous condition, etc., was, as I have 
said, of the most far-reaching significance to the biologist. The formation 
of permanent or semi-permanent suspensions and the demonstration that 
conditions of equilibrium could be reached in such systems followed by the 
recognition and careful descriptive characterization of sols and gels as 
studied in vitro brought chemistry and cytology on a common ground. 
One of the most important results of the study of the colloidal condition is 
the recognition of the fact that the units in colloidal systems, especially 
those of proteids, carbohydrates, etc., are large enough to be distinguishable 
at least with our present microscopes. 
With the recognition that semi-fluid systems in physical-chemical equili- 
brium can be constituted of units larger than the molecules and within range 
of study at least with the ultra microscope, the possibility of assuming a 
complex meta-microscopic organization of the protoplasm in which the 
essentials of vital processes are carried on is made less plausible. These 
foam and emulsion structures are the first and most obvious characteristics 
of protoplasm which the microscope reveals. Even more, the evidence 
that in this colloidal condition the transition from liquid to solid, from sol 
to gel, tends especially to pass into an indefinite series of gradations gave 
a basis for the explanation of that mixture of the properties of solids and 
liquids which has puzzled students of protoplasm. In the light of the 
effects of temperature changes on the phases of a colloidal system the familiar 
biological phenomena of heat rigor, rigor mortis, protoplasmic coagulation, 
etc., could be at least paralleled by phenomena in vitro. The reversibility 
of the processes in certain cases and their irreversibility in others also parallel 
other familiar cytological data. 
The biologist could only demur when the chemist demanded that he 
describe the phenomena of plant form in terms of crystallography and the 
processes of nuclear and cell division in terms of the chemical reactions of 
substances in solution. But Rhumbler has made real progress in describing 
the form of the shells of Foraminifera in terms of surface tensions in an 
anomogenous semi-liquid system, that is, a system whose liquidity varies 
in its different parts so that the homologous surface tension angles are 
always equal though non-homologous angles may be widely different. 
To say that the chromosomes go into solution in the telophases and reappear 
as crystals in the prophases was palpably absurd, but to describe the change 
as the passage of a gel into the continuous phase of a sol and its reverse is a 
