480 STUDIES IN GENERAL PHYSIOLOGY 
IX. SUMMARY OF RESULTS 
1. The addition of small amounts of a very dilute acid 
or alkali brings about a great increase in weight (absorption 
of water?) in a muscle contained in a physiological sodium 
chloride solution. 
2. For the inorganic acids, HNO,, HCl, H,SO,, 
KaHSO,, NaHSO, (ina high degree of dilution) this increase 
in weight is solely a function of the number of hydrogen ions 
contained in the unit of volume of the physiological salt 
solution. Solutions of these different acids which contain 
the same number of H ions in the unit of volume bring 
about a quantitatively equal increase in weight. 
3. This simple relation does not hold for organic acids 
(acetic acid, lactic acid, malic acid). In these the effect of 
the anion or of the undissociated molecules makes itself felt. 
4, For the bases LiOH, NaOH, KOH, S1(OH),, Ba(OH),, 
this increase in weight is solely a function of the number of 
hydroxyl ions contained in the unit of volume of the 
physiological salt solution. Dilute solutions of these differ- 
ent bases which contain an equal number of hydroxyl ions 
in the unit of volume bring about an equal increase in 
weight. 
5. If the muscle is introduced into various solutions of 
NaCl the osmotic pressure of which is higher or lower than 
that of the muscle, it is found that the change in the weight 
of the muscle is not proportional to the difference between 
the osmotic pressure in the muscle and that of the surround- 
ing solution; in hypisotonic solutions the muscle increases 
in. weight more rapidly; in hyperisotonic solutions it 
decreases in weight more slowly than corresponds to the 
differences in osmotic pressure. 
6. The validity of Van ’t Hoff’s theory of osmotic pres- 
sure for these processes is proved by the fact that solutions 
of LiCl, KCl, RbCl, CsCl, MgCl,, CaCl,, SrCl,, and BaCl, 
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