501 
figure. Fig. 4c illustrates the experiment in which again 0.01 mer. 
of pilocarpin is given and afterwards 0.024 mgr. of atropin, i.e. 40 
times as much as in the preceding experiment; this atropin, however, 
has been in contact with rabbit’s serum, and now it can distinctly 
be observed that the action of the atropin is again reduced to less 
than '/,,. In fig. 4d 0.0015 mgr. of atropin is administered, i.e. much 
less than in fig. 4c; this atropin has also been in contact with serum, 
but in this case a little peptone (Warre) had been previously added 
to it. It is manifest that now the atropin-action is not nearly reduced 
to '/,,, from which it becomes evident that the addition of peptone partly 
prevents the adsorption of atropin by rabbit’s serum. That an existing 
adsorption can be loosened by the peptone appears from fig. 4e, 
where 0.005 mgr. of atropin has been added. This dosis is active, 
at least much more active than 0,024 mgr. of atropin was in fig. tc 
and this dosis of 0.005 mgr. of atropin is taken from a solution, in 
which the atropin had first been adsorbed by rabbit’s serum, and 
subsequently a drop of 5°/, peptone-solution had been added. So 
through the influence of peptone the existing adsorption had been 
partly abolished. Fig. 4f again tends to show that 0.0006 mgr. of 
atropin is still active. This is a control-experiment. 
Little is known as yet about the nature of the adsorbing substances 
in rabbit-serum. DöBLIN and FrEISCHMANN') found that the substance 
cannot be heated above 60°, also that it can be refrigerated and 
thawed again and even desiccated. It does not pass through a 
_ chamberlandeandle. At the dialysis of the serum the albumin group 
appeared to adsorb, the globulin group did not. When salting out 
they found the same result. 
We have endeavoured to learn more about the nature of this 
substance; thus far with very little result. Plasma of rabbits as well 
as serum seems to have a great adsorbing power; the blood- 
corpuscles, when washed out and suspended in a physiological 
salt-solution do not adsorb atropin. We also saw that although rabbit’s 
serum is very active, that of cats, men, horses, cows and goats is 
little active. We happened to have the disposal of a qnantum of 
rabbit’s serum, which had been reserved in Professor VAN CALCAR's 
laboratory for nine years in a sealed up glass tube; this serum has 
still a high adsorbent power for atropin. 
Finally we also learnt from special experiments that lecithin does 
not adsorb atropin, which accords with Srorm van LEeEuWEN’s result 
with respect to pilocarpin and lecithin. It may very well be that 
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