682 
BOTANY: O. L. RABER 
If we could observe our own Galaxy from a sufficient distance, it 
would probably have many resemblances to a spiral nebula (compare 
Easton's work on the Milky Way as a spiral). The evidence adduced 
that rings or whorls of occulting matter are of very frequent occurrence 
in the spirals is a point of great weight in connection with the evidences 
of similar matter in our Galaxy. In particular, the results may be 
regarded as bearing very directly on the only hypothesis which seems to 
explain the peculiar grouping of the spirals: that the invisibility of 
spiral nebulae in our Galaxy and their scarcity in the regions contiguous 
to our Galaxy are due to the presence of occulting matter in the outer 
confines of our stellar system. 
THE SYNERGETIC ACTION OF ELECTROLYTES 
By Oran L. Raber 
LABORATORY OF PLANT PHYSIOLOGY. HARVARD UNIVERSITY 
Communicated by G. H. Parker, October 20. 1917 
Numerous cases are reported in which a mixture of toxic salts is less 
harmful than either salt used by itself. This has been called antagonism 
since one salt antagonises the action of the other. Theoretically the 
^opposite action may exist, in which one salt increases the toxicity of the 
other. I suggest that this be called synergy. Very few cases of this are 
reported^ and in some instances there is difficulty in deciding whether 
they really belong in this category because we lack data to show what 
the result would be if each salt acted independently of the other. Such 
data can be secured only by studying the effect of each salt separately 
and at various concentrations. 
Studies of this sort have been made by me during the past summer 
at Woods Hole. The marine alga, Liminaria Agardhii Kjellm., fur- 
nished the experimental material. The behaviour of this plant with ref- 
erence to antagonistic salts has been studied by Osterhout^ who em- 
ployed the method of electrical conductivity for this purpose. This 
method was used by me in his investigations. As the details of the pro- 
cedure are the same as in the experiments of Osterhout it is unnecessary 
to describe them here. 
The salts used were the purest obtainable and the distilled water was 
not toxic to delicate test objects. 
As I was primarily interested in the effects of anions the action of a 
series of sodium salts was investigated. These included the chloride, 
iodide, bromide, nitrate, acetate, sulphocyanide, sulfate, citrate, and 
