550 STUDIES IN GENERAL PHYSIOLOGY 
pressure of a NaNO, and KNO, solution which is just able 
to prevent growth in Spyrogyra is lower than that of a sugar 
solution which renders growth impossible. Hence he con- 
cludes that NaNO, is not harmless for Spyrogyra.’ In this 
case, of course, the concentration of Na ions was much 
greater than in the blood or in sea-water. It is, however, 
easy to give striking illustrations of the fact that a pure 
NaCl solution is a strong poison. In a former paper I have 
shown that Fundulus, a marine fish, can endure an astonish- 
ing increase in the concentration of sea-water. An addition 
of 5 per cent. NaCl to sea-water does not injure the animal.’ 
I selected it for testing my conceptions concerning the metal 
proteids. I found that it dies in a short time in a pure NaCl 
solution of the same concentration as that in which this salt 
exists in the sea-water.” In 3n solutions of NaCl which 
were diluted with various quantities of distilled water, the 
animals lived the longer the greater the dilution was, and in 
distilled water the young fish lived indefinitely. The 
following table shows the duration of life of these fish in 
pure NaCl solutions of various concentrations: 
TABLE I 
AVERAGE DURATION OF LIFE OF YOUNG FUNDULUS IN PURE NaCl SOLUTIONS OF 
DIFFERENT CONCENTRATION 
Nature of the Solution Duration of Life 
1O0:e:c2 Fn: Na€l wae cee ces gains aS Ea os Less than 12 hours 
90 “« + 10c.c. distilled water About 24 hours 
80 ty 6 + 20 6 “ 30 6“ 
50 “ (73 + 50 6c “ 40 “ce 
90 «= “ + 80 “ “ 60 « 
10 66 6c + 90 “ iT 72 6 
OQ» * +100 $ Still alive after 10 days 
1TRvE, Botanical Gazette, 1898, p. 407. 
2LogEB, Archiv fiir die gesammte Physiologie, Vol. LV (1894), p. 530. 
3For these experiments the young fish which had just hatched were used. As 
they were less than a centimeter long, their mass was small compared with the 
volume of the solution. 
Digitized by Microsoft® 
