Physiology. — “On Superficial and Internal Processes”. By Pvof. 
H. ZWAARDEMAKER. 
(Communicated at the meeting of December 23, 1921). 
In 1908 (1) I discussed, in collaboration with M. C. DeEKHUYZEN, 
the hypothesis that animal tissues are to be conceived as a system 
of co-existent phases. Phases have been defined there as a sondition 
of the substance homogeneous at a given moment. In life the statio- 
nary current of metabolism with its periodic fluctuations passes 
through such a system. Once every 24 hours the condition ap- 
proaches nearly the equilibrium during profound sleep. 
In such a system it is especially the boundaries of the phases 
that are important, for directly when action sets in chemical pro- 
cesses manifest themselves near the boundaries. This may be expected 
a priori and is proved a posteriori by the great importance physio- 
logy has to attach to surface-tension and to membrane-potentials. 
Such important phase-boundaries in a tissue are, generally speaking: 
a. the cell-surfaces, 
6. the contours of the nucleus, 
c. the contours of the mitochondriae, 
d. the mantle-, and contact-planes of double-refracting pieces of fibrils, 
e. the contact-planes of the neurobions of Cajal. 
Also in the phases themselves processes occur, as physiology usually 
assumes. To these processes belong i. a. stationary metabolism, just 
now alluded to, heat-production, growth. 
A general physiology of the phases has to distinguish between 
superficial and internal processes. 
I have had many occasions to occupy myself with the first 
category, since all processes in which animal radio-activity comes 
into play, belong to the sub-superficial processes, while the second 
category i. e. the internal processes comprises all processes to which 
Baas Brcxine (3) has lately applied the theory of Perrin in such a 
signal way. 
This should not tempt us to generalize prematurely and to advance 
the hypothesis that in nature all superficial processes have corpus- 
cular radiations for catalyzator, and all internal processes electro- 
magnetic vibrations, and that beyond these radiations there are no 
other biological catalyzators. We do not feel justified in deducing 
