[From the American Naturalist, Vol. V, October, 1871.[ 
EXPERIMENTS WITH VIBRATING CILIA. 
BY JEFFRIES WYMAN, M.D. 
The motions of vibrating cilia, and their action on the water 
around them, are among the most beautiful sights shown by the mi- 
croscope. They are best seen on the respiratory surfaces of both 
land and aquatic animals, and of the last, the gills of the Mytili 
are especially favorable for examination. In such cases, the effects 
are confined to the movement of the secreted mucus, or of the 
surrounding water, and the particles floating in it, while in 
others the cilia cover the outer surface and become the chief or- 
gans of locomotion, as in the Infusoria. In the eggs of Radi- 
ates and Molluscs, as in the remarkable phenomenon of the rota- 
tion of the yolk, much larger masses are moved, and among 
Batracliians, the yolk, soon after impregnation and segmentation, 
being large enough to be easily watched with the naked eye, is 
seen to revolve steadily under ciliary influence. Even the re- 
cently hatched larvae of frogs and toads are carried along bodily 
by the same agents distributed over the whole outward surface, 
without the slightest aid from the muscular system. In all of 
these instances, however, although in some the mass moved is con- 
siderable, the motion takes place in a fluid, of nearly the same 
specific gravity as the objects, and so the force required to give 
the motion is exceedingly small. Indeed everything serves to 
give the impression that cilia are capable of exerting only the 
Entered according to Act of Congress, in the year 1871, by the Peabody Academy of 
Science, in the Office of the Librarian of Congress, at Washington. 
AMUR. NATURALIST, VOL. V. 
611 612 
EXPERIMENTS WITH VIBRATING CILIA. 
most delicate efforts. There are several ways in which their 
effects may be shown without the aid of the microscope, but 
the most common is that of sprinkling some light powder over 
the ciliated membrane, from which the powder is soon swept away. 
The object of this paper is to explain some other methods adapted 
to class experiments having the same end in view, but by which 
motion is imparted to much larger masses, and also to show that 
in some instances a much greater resistance can be overcome than 
has generally been supposed possible. 
I. Experiments in water. — For these the gills of Unios and 
Anodontas are well suited. Their cilia are quite active, and vi- 
brate in such directions, that on the inner gill the motion is from 
the free edge, and on the outer to it, facts which the experimenter 
should keep in mind. If an inner gill is cut away from its at- 
tachment and laid on the bottom of a flat dish, its cilia acting as 
legs, it will soon begin to move with its free edge forwards, and will 
in the course of time, travel the entire length of the dish. We 
have seen a whole gill move ten inches in four hours. Under simi- 
lar circumstances the outer gill will move with its base or cut edge 
forwards. This difference depends, as will be readily seen, upon 
the fact that the cilia of the two gills vibrate in opposite directions. 
The result of ten experiments gave the rate of motion of a 
piece of gill measuring 12mm. by 14mm., 6mm. a minute. If two 
outer gills are laid with their free edges towards each other they 
will at once begin to approach, and it frequently happens after 
meeting that one crawls directly over the other. 
Another and more striking experiment which shows the reaction 
of cilia on each other may be made as follows. Fasten a gill to a 
piece of cork under water, and place upon it a portion of a sec- 
ond gill about a half inch square. If this piece is so placed that 
the cilia vibrate in the same direction with those of the gill below, 
it will remain stationary, or nearly so, since the cilia offer no re- 
sistance to each other. If now the upper piece is reversed so 
that the cilia vibrate in opposite directions, the upper piece will 
move with double the speed and through twice the distance in a 
given time that it would with its own cilia alone, for while the 
lower cilia move the upper piece through a certain space, the cilia 
of the upper piece also move this in addition through an equal 
space. A third form of this experiment consists in placing the 
upper piece so that its cilia vibrate at right angles to those of the 
lower. In this case, while the lower cilia tend to move the upper EXPERIMENTS WITH VIBRATING CILIA. 
613 
piece from side to side, those of the upper tend to move this 
lengthwise of the lower. The direction which the upper piece 
takes, is a resultant one, viz., intermediate between the two. 
II. Experiments in air. Though the tissues of the gills of 
Unios and Anodontas are quite soft and incapable of resisting 
other than very light weights, they will nevertheless carry small 
discs of paper supporting a bristle, on the top of which is a small 
pellet of cotton or a flag of tissue paper. In order to show the 
flag more distinctly, a board painted black should be nailed to the 
edge of the one on which the gill rests, to make a back ground. 
With this precaution the experiment may be seen over a large 
room. To mark the distance traversed, a pointer of white paper 
should be set up on the board supporting the gill and at the be- 
ginning of the experiment, the end of the pointer brought in con- 
tact with the end of the flag on the gill. When left to itself, the 
disc on the gill with its flag at once begins to move to the opposite 
side and the flag is seen to recede from the pointer. The distance 
traversed may be increased to several inches, by placing two or 
more gills side by side, the free edge of the first slightly overlap- 
ping the cut edge of the second, etc. 
The mueous membrane from the roof of the mouth of frogs, is 
much more solid than the gills of Unios, and the cilia vibrate 
with much greater force. Different ciliated membranes exert very 
different degrees of foree, but we have found none better suited 
for experiments than that just mentioned ; especially, when taken 
from the mouth of the bull frog which gives a large surface. It 
has the advantage, too, of keeping up its activity for twenty-four 
hours or more, after being detached from its natural connections, 
if only kept cool and moist. For moistening it water answers 
sufficiently well, but the serum of the blood of the frog is still 
better. 
The attention of the writer was first called to the possibility of 
moving weights much larger than was supposed possible by notic- 
ing the ease with which a piece of skin which was accidentally 
placed upon the ciliated membrane was swept off. By loading 
the piece of skin with weights the mass moved was found to be 
unexpectedly large. 
In making experiments for the purpose just mentioned we have 
adopted the following method. The mucous membrane, being 
carefully disseeted from the roof of the mouth, is pinned to a 
board. A piece of skin from near the throat of the frog, and 614 
EXPERIMENTS WITH VIBRATING CILIA. 
from one-third to half an inch square, is placed upon this mem- 
brane with the inner surface in contact with the cilia, it being kept 
in mind that these vibrate from before backwards towards the 
throat. On the skin may be placed a plate of lead of somewhat 
smaller size. This serves as a vehicle to which weights may be 
added at will to increase the load, and also as a drag, to set in 
motion the instrument described farther on. To show the distance 
through which the load is carried, the flag and pointer may be 
used as in the case of the gills before described. Pains should be 
taken to have the board on which the experiment is made perfectly 
horizontal, otherwise a sliding motion, especially when heavy 
weights are used, may come in to vitiate the experiment. 
Although the results are not uniform, the following will give some 
idea of the force exerted, as shown by the time in which and the 
distance through which the weight was carried. The mean of four 
experiments shows that a weight of 1.300 grams was carried 
15mm. in 61.2 seconds, or about 4mm. per second, the weight rest- 
ing on a surface 12mm. square. A weight of thirty-three grams 
resting on the same amount of surface, a mean of four experi- 
ments gave a distance of 6.6mm. per minute. We have seen 
forty-eight grams resting on a surface 14mm. square, moved, 
though very slowly, across the whole length of the membrane, but 
the exact time was not noted. Dr. H. P. Bowditch has repeated 
these experiments in the laboratory of Ludwig at Leipsic with 
even heavier loads. 
Finding that so much force was exerted, the idea of utilizing it 
was naturally suggested, and after various trials the following in- 
strument was devised for this purpose, in which the direct motion 
produced by the cilia was made to give rise to a rotary one. The 
instrument consists of two light toothed wheels (see figure), the 
larger 30mm. and the smaller 5mm. in diameter. To the axis of 
the first is attached a small drum 5mm. in diameter, around which 
is coiled a thread of the finest and most flexible cotton. The axis 
of the smaller wheel is prolonged through the frame in which both 
wheels move, and carries on its end an index made of two bristles 
inserted into a central piece of cork, which is attached to the 
axis. On the end of each bristle is a very light paper pointer. 
The whole length of the index is 110mm. but may be made longer 
or shorter than this, as may be convenient to the experimenter. 
Behind the instrument there should be a small black board at- 
tached to the base on which the frame rests, to serve as a back- EXPERIMENTS WITH VIBRATING CILIA. 
615 
ground against which the pointers are seen. The instrument is of 
sufficient delicacy to be moved by a weight of from owe- hundred to 
one hundred and twenty millegrams or of from seven to eight 
grains. All that is necessary to make an experiment is to attach 
the end of the thread coiled around the drum to the hook on the lead 
which rests on the piece of skin, which in turn rests on the mem- 
brane. The proportions of the Avheels are such, that when the 
load resting on the membrane is carried through a space of 7mm. 
the index makes two whole revolutions, and the point of the in- 
dex moves through a space of about two feet. One complete 
revolution is effected in about thirty seconds. This motion may 
be easily seen over a large lecture room. 
Fig. 110. 
Description of the diagram, a. A movable block of wood to 
which the ciliated membrane is pinned, b. Ciliated membrane. 
c. Piece of skin resting upon it. d. Plate of lead with a small 
hook to which the thread coiled around the drum is attached, e. 
and /. Pointers, one resting on the lead and the other on the 
board to which the instrument is fastened ; these are made of wire 
inserted into a base of wood or cork, and carry each a piece of 
paper or thin card; both are movable. The wheels are toothed. 
Attached to the axis of the large wheel is the drum, and to the 
projecting portion of the axis of the small wheel is the index. 
This figure is one-half the size of the instrument. The base on 
which the instrument rests, should be made longer than in the 
figure so that the block to which the membrane is attached may be 
farther off from the wheels.