PRIMARY INHIBITION OF CILIARY MOVEMENT 407 
the electrode was quite immersed, was somewhat lower than the 
height of the sea-water in the cuvette. The insignificant differ- 
ence of hydrostatic pressure tended thus to drive the sea-water 
over to the zine solution, but prevented any flow of liquid in 
the opposite direction. In the solution of zinc sulphate was put 
a zine rod with a set-screw for the connecting wire. For each 
experiment a fresh clay filling was prepared and the zine rod was 
rubbed clean with emery-paper. 
Each of the tube electrodes was placed at a short end of the 
cuvette. The animals were manoeuvred exceedingly carefully 
with rounded glass rods so that their longitudinal axis coincided 
with the line of connection between the electrodes. When the 
cathode was outside the sensory pole, the current is called in the 
records ‘longitudinal oro-central current.’ When the direction 
is the opposite one, it is called ‘centro-oral current.’ A battery 
of ten Jungner accumulators was used as source of the current. 
By means of an element calculator it was possible to take the 
current from such a number of these as was necessary for the sepa- 
rate experiments. On a few occasions it would have been desir- 
able to have had a stronger battery at my disposal. When in 
some cases a continuous alteration of the strength of the current 
was necessary, the rheonome of v. Fleischl was used. To meas- 
ure the current a milliamperemeter was employed (Reiniger, Geb- 
bert and Schall), on which the strength of the current could be 
read up to 5 milliamperes with an accuracy of 1/20 m. amp. 
and between 5 and 50 milliamperes with an accuracy of 1/10 
m. amp. From our knowledge of the strength of the current in 
the circuit on a given occasion and the level of the liquid in the 
cuvette on the same occasion it is possible to calculate the den- 
sity of the current in milliamperes per square centimeter (m. 
amp./em.?) for the column of liquid between the electrodes on 
the same occasion. 
