920 
of lecithin-action because, as already mentioned, in many cases the 
lecithin was inactive. We examined this in 13 experiments, 5 of 
which yielded positive results, i.e. 5 times the lecithin intensified 
the pilocarpin-action; 6 times, however, the result was negative, 
once it was doubtful and in one case the pilocarpin-action had 
weakened after the lecithin. 
We see, then, that though lecithin undoubtedly intensifies the 
pilocarpin-action in some cases, this does not occur always. For the 
present we cannot state the reason. The explanation may lie in this 
that — as said above — we invariably added lecithin only when, 
after a repeated addition of pilocarpin, the gut had obtained its 
maximal sensitivity to this poison. Probably the lecithin would 
intensify the pilocarpin-action with greater regularity, if it were 
administered in an earlier stage, when the gut is still less sensitive 
to this poison. In that stage, however, it would be impossible to 
obtain accurate results. 
Influence of cerebron on the sensitivity of the cat-gut to pilocarpin. 
The influence of cerebron on the pilocarpin-action had to be 
examined in two directions, as was the case also with the influence 
of Witte's peptone, to be discussed lower down. STORM VAN LEevwrEn’s 
inquiry, alluded to above, had shown that rabbit’s serum, and also 
organs of the rabbit, contain substances capable of adsorbing pilo- 
carpin physically. 
Endeavours to determine the nature of these substances have 
failed up to now. It appeared from the inquiry referred to that. 
cholesterin and lecithin are not the substances looked for. 
It was necessary, therefore, to examine also cerebron (and Witte’s 
peptone) in this direction. We proceeded as follows: we waited till 
the gut’s sensitivity to pilocarpin had become constant; then pilo- 
carpin was administered and subsequently pilocarpin + cerebron 
and finally again pilocarpin alone. In this way we could ascertain 
whether the addition of cerebron to the pilocarpin-solution (the 
cerebron was in contact with the pilocarpin for from ‘'/,—2 hours, 
before it was added to the gut) lessens the action of it, and we 
could also ascertain whether, after the cerebron + pilocarpin had 
been washed ont again, the following dosis of pilocarpin acted more 
forcibly than before, whereby it could be proved whether or no 
cerebron intensified the action of pilocarpin. 
Because only a small quantum of cerebron was at our disposal, 
we undertook only three experiments. It appeared from them that 
