Histology. — “An Inquiry into the Distribution of Potasstum- 
compounds in the Electric Organ of the Thorn-back (Raja 
Clavata).” By M. W. WOERDEMAN. (Communicated by Prof. 
H. ZWAARDEMAKER). 
(Communicated at the meeting of October 30, 1920). 
On Prof. ZwaarDEMakER’s suggestion I have latterly examined 
different tissues and organs microchemically on the presence of 
potassium-compounds. I intend to discuss the method and the results 
of this inquiry more in detail; for the present I will publish 
only my experience in the investigation of the electric organ of the 
Thorn-back (Raja clavata). 
ZWAARDEMAKER’S researches established that the function of organs, 
perfused artificially with a salt-solution, largely depends on the 
potassium-content of that solution, and that the potassium, being a 
weakly radio-active element, plays such a prominent part in the 
origin of the organic actions, on account of its very radio-activity. 
It may be supposed, therefore, that the potassium compounds which 
are normally to be found in the organs of animals or plants, take 
an important part in the normal functions of these organs. We 
presume, therefore, that information concerning the presence or the 
absence of potassium-cumpounds in certain cells, tissues, or organs 
will be gladly received. 
Now, through chemical examination the quantum of potassium, 
contained in various organs, has already been determined with great 
accuracy. From this examination we do not learn, however, where 
in the organ the potassium-compounds are located.  MAcALLUM namely 
has detected that in a number of tissues and organs the potassium- 
salts are not distributed at random and irregularly, but that they 
often occur there at definite places, bound to quite definite structures. 
MacaLLum’s') reagent on potassium-compounds is a modification of 
the mixture used for the first time by Dr Koninck?). MACALLUM’s 
mixture of cobalt-salt and sodium-nitrite, added to a potassium-salt 
‘) A. B. Macatium. On the distribution of potassium in animal and vegetable 
cells. Journ. of Physiol Vol. XXXII, 1905 and Die Methoden und Ergebnisse der 
Mikrochemie in der biologischen Forschung. Ergebn. der Physiologie, Jrg. 7 
1908, p. 552. 
3) DE Koninck. Zeitschr. f. analyt. Chemie. Bnd. 20. 1881, p. 390. 
