IoN-PROTEID COMPOUNDS 549 
address of ion-proteid compounds, and I only need to quote 
the following sentence in order to show how far his concep- 
tions and mine agree. ‘We cannot doubt the general 
existence of ion-proteid compounds in the living organism. 
We have even urgent reasons for assuming that all the pro- 
teids of the protoplasm exist there only in combination with 
ions.’ I shall have a chance to discuss his views further 
when the full account he promises of his experiments appears. 
These introductory remarks may suffice for the present. 
I will now report on a series of experiments which were 
undertaken on the assumption of the existence of ion pro- 
teids, and the possibility of changing the qualities of tissues 
by changing the relative proportions of ions in the tissues. 
II. EXPERIMENTS ON FISH 
If it be true that life-phenomena depend upon the pres- 
ence of a number of various metal proteids (Na, Ca, K, and 
Mg) in definite proportions, it follows that solutions which 
contain only one class of metal ions must act as a poison. 
The reason for this is that the one class of metal ions will 
gradually take the place of the other metal ions in the ion 
proteids of the tissues. Even a pure NaCl solution must 
thus be poisonous, although this salt permeates all our tissues 
and is the main constituent of the inorganic matter of the 
ocean. I have looked through the literature in vain to find 
facts which corroborate this view. I found only the follow- 
ing data: Ringer and Locke’ mention the fact that in NaCl 
solutions the contraction curve of a muscle may show slight 
variations, and Locke adds that the same is true for certain 
electric phenomena in the nerve. True has added another 
observation in this direction. It has been known for many 
years that if we put plant cells, for instance Spyrogyra, into 
a very concentrated solution of salts or sugars, the cells 
lose water and cease to grow. True found that the osmotic 
1 Locks, Archiv fiir die gesammte Physiologie, Vol. LIV (1893), p. 501. 
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