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stances (which are all soluble in fat) have on the mobility of phago- 
cytes and on the development of eggs may be regarded from the same 
point of view. 
But there is still more made clear by the above researches. It is 
namely a well-known fact that various narcotics applied in smaller 
doses have a stimulating effect and paralyze in greater quantities. 
ENGELMANN observed this already many years ago on vibratile cilia 
and also as regards the nervous system we know of Chloroform, 
Aleohol, Aether that when first administered, that is to say when 
they have entered into the nerve-cells in small quantities, they cause 
excitement, but produce insensibility when a greater amount of the 
substance has penetrated into the cells. As far as we know this 
contrast has never been explained, but when viewed in connection 
with our experiments the phenomenon becomes clear. 
Two factors must be distinguished in the working of the narcotic: 
in the first place it must be dissolved in the lipoid membrane, 
secondly after having entered into the protoplasm in sufficient 
quantities it will produce its narcotic effect. But already before the 
latter has taken place the lipoid membrane has undergone a decrease 
in its surface tension and the stimulating effect manifests itself. The 
excitement disappears of course when the protoplasm has been 
paralysed *). 
Hence we see that, what was observed about phagocytosis deserves 
ves our attention also from a general point of view. We do not 
mean to say, and this must be distinctly understood, that all sub- 
stances dissolving fat have the same effect on various cells ; far from it. 
In the first place the word “lipoid” is a collective notion, and it 
may be expected that with different cells the composition of lipoid 
will be quite different, and also its solubility in one and the same 
fat-dissolving substance. Secondly not all substances penetrating 
into cells, dissolve fat or can be mixed with it. Urea may serve as 
an instance. 
And thirdly, it need hardly be observed that the power of asub- 
stance to penetrate through the lipoid membrane will by no means 
determine its further physiological and pharmacological effeet. This 
will be chiefly dependent on the chemical structure of the cell-con- 
tents, which are different in the different kinds of cells. 
1) The paralyzing effect of narcotics on protoplasm Manerrip is inclined to 
attribute to want of oxygen, caused by the decreased permeability of the cellipoids 
to this gas. (Prtuger’s Archiv. 131, 1910, p. 464, 
