Electricity and galvanism produce no visible effect. A powerful discharge from a Leyden jar was made to pass through the River-mussel by Purkinje and Valentin without-causing any change in the ciliary motion. Portions of the external gills of the Tadpole were subjected by myself to the same experiment and with a similar result, except when the surface. was abraded, which occasionally happened with 'a strong discharge. I have exposed portions of the gill of the River-mussel while viewed with the microscope, to the influence of a'galvanit battery of twenty-five pairs of three-inch square plates, charged with solution of salt, without being able to perceive the slightest effect on the motion of the cilia. The authors above men. tioned obtained a similar result, both in the. Mussel and the domestic Fowl.
The effect of temperature is different in warm and cold-blooded animals. In the former, ac cording to Purkinje and Valentin, the motion stopped on exposure to a temperature of 43° F. while it went on at 540 F. On the other hand they found that in the Fresh-water Mussel it was not affected at 320 F.; and I found the same to be true of the Tadpole. A portion of the gills of the River-mussel, which I kept for five minutes in water at 960 F. slimed no change.
Acids, saline solutions, and other substances applied to the parts, differ in their effects ac cording to the kind of animals submitted to experiment. Thus, for example, fresh water instantly arrests the motion in the Marine Mol lusca, and also in other marine animals in which I have tried its effect, though a satu rated solution of sea-salt destroys it both in salt and fresh-water species. Purkinje and Valentin state the effects which they. found to result from the application of. various sub stances, but erroneously conceiving, from some preliminary trials, that the same substance produced the same effect in all animals, they confined their experiments to the Fresh-water Mussel. According to their experiments,which were made with a great many different sub stances, most of the common acid, alkaline, and saline solutions, when concentrated, arrest the motion instantaneously ; dilution, to a degree varying in different substances, pre vents this effect altogether, and a less degree of dilution delays it. The same is the case with alcohol, wther, aqua laurocerasi, sugar, and empyreumatic oil. Kreosote, muriate of baryta, siflphate of quinine, infusio pyrethri, and muriate of veratria, act less intensely. Hy drocyanic acid and watery solutions or in fusions of belladonna, opium, capsicum, ca techu, aloes,. musk, gum-arabic, acetate of
morphia, and nitrate of strychnia, produce no effect whatever. They accordingly infer that the substances affect the motion only in so far as they act chemically on the tissue.
The result of my own experiments differs from theirs in some points. In the River-mus sel I found that hydrocyanic acid, containing ten per cent. of pure acid, invariably destroyed the motion. Solution of muriate of morphia, of medicinal strength, also arrested the motion in the Mussel, but not in the Batrachian larv2e. The motion on the gills of these larvm also continues unimpaired in water deprived of air by boiling, or distilled, or impregnated with carbonic acid; a sufficient proof, it may be remarked, that it is independent of the che mical process of respiration.
In regard to the effect of animal fluids, the authors already mentioned state that bile ar rests the motion, while blood has the property of preserving it much beyond the time that it lasts in other circumstances, at least in verter brated animals ; thus it continued three days in a portion of the windpipe of the Rabbit, which had been kept in blood. But it is sin gular that blood or serum, whether of Quadru peds, Birds, or Reptiles, has quite the opposite effect on the cilia of invertebrated animals, arresting their motion almost instantaneously. Albumen and milk also possess the conserva tive property, though in a less degree.
8. Effects of inflammation.—Purkinje and Valentin excited inflammation artificially in the nose and vagina of rabbits, and are in clined to conclude from their experiments, which however are not numerous, that inflam mation arrests the motion.
9. Of the power by which the cilia are moved.—It may next be inquired by what means or by what power the cilia are moved ; and, in particular, whether their motion, like other visible movements in the animal body, is effected by muscular action.
Dr. Grant,4' reflecting that in the Beroe a vessel conveying. water runs beneath each row of cilia, and, that, according to M. Audouin, in an allied genus of animals the water enters the cilia, is disposed to liken the motion of the cilia to that of the feet of the EchinoderL mata. He seems accordingly to think it pro bable that the cilia are tubular organs, which are distended and protruded by the injection of water into them from elastic tubes running along their base, in which the water is conveyed by successive undulations.