548 STUDIES IN GENERAL PHYSIOLOGY 
point, they gain in significance. They teach us that we can 
impart to a tissue new properties by changing the quality 
and the relative proportions of the ions in combination with 
the proteids. The characteristic qualities of every tissue 
are partly due to the fact that its ion proteids contain certain 
ions in definite proportions. Any change in this proportion 
is accompanied by a change in the properties of the tissue. 
Ten years ago I started upon experiments in which I 
substituted at desire one organ for another or transformed 
one organ into another (heteromorphosis). The agents I 
used for this purpose were various forms of contact, gravita- 
tion, and light. But the number of animals in which the 
phenomena of heteromorphosis could be controlled was 
rather limited. I concluded at that time that it would be 
necessary for the development of this technical or con- 
structive side of biology to fina a more elementary point of 
attack. The ion proteids, on account of the ease with which 
their properties can be changed by a change of their ions, 
seemed to offer the desired opportunity. I therefore decided 
to devote last summer at Woods Hole entirely to experiments 
in this direction. Marine animals which live in a medium 
having a high concentration of ions seemed to offer better 
opportunities than fresh-water or land animals. 
A brief report of one part of the summer’s work was 
published in this periodical.’ Since then Dr. W. Pauli, of 
Vienna, has published an address in which he reaches similar 
conclusions on ion proteids independently.’ His conceptions 
are based on experiments upon the physical qualities of 
proteids. His address appeared too late to influence me in 
my work or my ideas, but the clearness of his results and 
statements was a very welcome support. He speaks in his 
1 American Journal of Physiology, Vol. III, p. 135. 
2W. Pauut, Ueber physikalisch-chemische Methoden und Probleme in der 
Medizin (Wien, 1900); and ‘‘Ueber die physikalischen Zustandanderungen der 
Eiweisskorper,” Wiener akademischer Anzeiger, October 12, 1899. 
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