( 960 ) 
is of such a peculiar character. The criticism of the methods for 
the purification of these substances, the characteristics of their purity, 
the question whether the water contained in imbibing erystals may 
be put — at least in part — on a par with the water of crystal 
lisation of inorganic salts (as pretended by Hoppr SEYLER *) and others 
in the case of oxyhaemoglobin crystals), the question whether the 
molecular weight of the imbibing substances can be determined from 
the decrease of their water vapour pressure, and so many other 
questions of that kind, are problems which the physiologieal chemist 
has, so to speak, to face daily, but which cannot be treated fully 
before the quantitative laws of swelling, and a due explanation of the 
same shall have been discovered. 
But relatively litthe being known of this matter at that time, | 
have been engaged since the summer of 1904 upon an extensive 
research in order to get a better insight into these quantitative laws 
and their explanation. Very soon, some remarkable regularities and 
analogies were brought to light. I thought it desirable, however, not 
to publish these results before they had been contirmed so repeatedly 
that they could not be looked upon as being merely accidental. 
in October 1906 1 had found the analogy now described in this first 
publication, and communicated the same to my teachers Profs. H. W. 
Bakutis RoozrBoom and A. Sirs. In this paper I will give only 
a brief and partial account of the experiments carried out. For 
experimental details and the literature on the subject the more extended 
publication which will appear shortly, should be consulted. 
Short description of the phenomena of swelling. 
Before describing the researches on imbibition it appears to me 
desirable to point out, briefly, which phenomenon I have studied, 
from which similar, but yet different, phenomena it must be distin- 
euished, and in which substances it is met with. This seems to me 
particularly desirable because these facts are sometimes mentioned 
in physics and chemistry under another name. 
2\ 
Bv swelling or imbibition power*) the biologists understand the 
1!) Cr. ScHärFeRr’s Textbook of Physiology, [. p. 205 (1895). 
2) The majority of investigators understand by imbibition power the same 
as swelling power. REINKE (HANSTEIN’S Botan. Abh. [V, p. 2 and 3) differs 
from this view; his idea of imbibition power includes porosity as well. I do not 
