M. Marey states that he succeeded in obtaining a photograph of the gilded wing of an insect, which, though not absolutely at liberty, could fly at a comparatively high rate of speed. The photographs of the trajectory of the wing of an insect are very interesting. A wooden box was lined throughout with black velvet. The bottom of the box, a simple disk supported by a foot piece, was placed in position; the periphery of the space was covered with a white material, leaving between it and the central disk an annular track covered with black velvet. It was around this annular track the insect was made to fly. A needle stuck in the middle of the disk served as an axis for a revolving beam and its counterbalance. This beam consisted of a straw, and at the end of it was fixed a light pair of forceps to hold the insect. The dragon fly commenced flying around the track at a very rapid rate, drawing the straw after it. The gold spangles passing through his wings described a trajectory which was easily photographed.
FIG. 27.—MOTIONS OF THE DORSAL FIN OF THE SEA-HORSE.
The chronophotography of insects by the use of a moving film has been also accomplished by means of very ingenious apparatus. In some cases the insects were held in forceps, and in other cases they were allowed free flight in a cardboard box.
“Comparative locomotion,” which is rendered possible by chronophotography, might almost be called a new science. It is, at any rate, an important adjunct to the studies of the zoölogist. The researches of M. Marey upon the different terrestrial mammals, birds, tortoises, lizards, frogs, toads, tadpoles, snails, eels, fish, insects, and arachnids are of the greatest possible value and interest. The applications of chronophotography to experimental physiology are numerous. It supplements the information obtained by the graphic methods. It has rendered possible the photography of the successive phases of cardiac action in a tortoise under condition of artificial circulation. The mechanism of cardiac pulsation has also been studied by its means, as well as the determination of the centers of movements in joints.
It has been found that chronophotography could be applied not only to objects of considerable size, but to those of microscopic size as well. Special arrangements of apparatus are necessary for this purpose. By its means the retraction of the spiral stalks in vorticellæ, the movement of the blood in capillary vessels, and the movements of the zoöspores in the cells of conferva have been determined.
FIG. 28.—MOTIONS OF THE COMATULA.