PRIMARY INHIBITION OF CILIARY MOVEMENT 409 
2. Frequency without any current, 10/12 sec. = 50 per min. 
With maximal current (indicated strength 100), frequency 10/14.5 
sec. = 41 per min. 
3. Frequency without current, 10/8.5 sec. = 71 per min. 
With current of the same strength as in 2, frequency 10/12 see. 
= 50 per min. 
We thus see that there was no alteration with the weaker cur- 
rent; the stronger one, on the other hand, was followed by some, 
though only very slight, reduction of the frequency. 
Under the influence of a stronger alternating current I have in 
other experiments on Beroé observed a contraction of the body 
of the animal with a drawing in of the rows and secondary inhi- 
bition of the ciliary movement. 
3. Beroé, 23 mm. in length, transferred 5h. 7 m. from the aqua- 
rium, where it swims about, to a cuvette containing sea-water at 
a temperature of 17°C. The animal takes up the usual horizontal 
position at the bottom of the cuvette and hasa slow ciliary move- 
ment in the four lower rows, a more rapid one in the four upper 
ones. 
The threshold for total inhibition of the ciliary motion during 
five seconds under the influence of a longitudinal oro-central cur- 
rent is determined by using an unpolarizable liquid resistance, 
which is regulated by an assistant, who also reads the milliam- 
perometer. 
5h. 20m. Inhibition threshold’ at 1.47 m.amp./cm.? 
5h. 24m. Inhibition threshold at 1.60 m.amp./em.? 
5h.40m. The animal is transferred to another cuvette con- 
taining sea-water with 0.1 per cent of chloral hydrate added. 
5h.44m. The animal has a very rapid ciliary motion and 
takes up a vertical position at the bottom. 
5h.56m. The ciliary movements have become considerably 
slower. On one of the most rapidly striking rows the number 
of the waves was found to be 30/23 sec. = 78 per min. 
6 h. Electrodes are immersed. With a longitudinal oro- 
central current total inhibition is now first attained at 2.47 
m.amp./em.2 When the current is broken, it appears that the 
first waves dies out at a rather short distance from the sensory 
