489 
1. the organs of the animal may not be sensitive to the poison. 
(StravuB') demonstrated not long ago that to this the resistanee of 
the rat to strophantin is to be ascribed). 
2. the poison may probably be destroyed chemically in the body. 
3. the poison may be made inactive in the body of the animal 
in another way. 
The first supposition will hardly apply to the case under consi- 
deration, because although the: rabbit possesses a great power of 
resistance to atropin, the organs of this animal are very sensitive 
to this poison. It has been proved by Van Liprn pr Jrunw’s*) expe- 
riments that the action of atropin upon the surviving small intestin 
of the rabbit is about ten times stronger than its action upon the 
catgut. Besides, as already mentioned, CaLmerrn showed that an 
intracerebral injection of two mgr. of atropin into a rabbit induces 
death instantly. 
As appears from the inquiries by FrrIsCHMANN, Metzner and others, 
the second supposition has come true. Rabbit's blood can decompose 
atropin in vitro, but this decomposition proceeds comparatively slowly, 
and consequently not on such a large scale as to enable us to 
establish from it the rabbit’s resistance to atropin, when this poison 
is injected directly into the circulation. 
These considerations tend to support the third supposition, and in 
the experiments to be described now we have been able to demon- 
strate the high adsorbent power of rabbit’s serum for atropin; still it 
does not decompose it. 
In order to demonstrate in these experiments the inhibitory influ- 
ence of rabbit’s serum, we needed an accurate method for a physi- 
ological determination of the values of atropin-solutions. To this end 
we adopted the method expounded by Storm van Leruwen and van 
DEN BROEKE in a previous publication’). Their procedure was as 
follows: a certain quantum of pilocarpin is added to a surviving 
piece of catgut and hereafter the amount of atropin was determined 
that is required to abolish almost entirely the contraction of the gut 
generated by the pilocarpin. This method yields satisfactory results, 
1) W. Srraus. Ueber die Resistenz der Ratten gegen K-strophanten. Arch. f. 
exp. Path. und Pharmak. Bd 84, p. 228, 1918. 
2) v. LiptH pe Jeupe. Quantitatieve onderzoekingen over het antagonisme van 
sulfas atropini tegenover hydrochloras pilocarpini, salicylas physostigmini en 
hydrochloras muscarini op overlevende darmen van zoogdieren. Dissertatie Utrecht 1916. 
3) Storm VAN LEEUWEN and VAN DEN BROEKE. A quantitative inquiry into the 
antagonism pilocarpin-atropin on the surviving cat-gut. Proceedings Roval Acad. 
Vol. XXVIII, p. 1158. 
