. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . luding food. In a creature so high in the scale as thefrog we find the alimentary tract ciliated ; and in man himselfa portion of the respiratory tract is provided with ciliated cellsconcerned with assisting gaseous interchange, a matter of thehighest importance to the well-being of the mammal. As be-fore indicated, ciliated cells are found in the female generativeorgans, where they play a part already explained. It is a matter of no little significance from an evolutionarypoint of vie
. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . luding food. In a creature so high in the scale as thefrog we find the alimentary tract ciliated ; and in man himselfa portion of the respiratory tract is provided with ciliated cellsconcerned with assisting gaseous interchange, a matter of thehighest importance to the well-being of the mammal. As be-fore indicated, ciliated cells are found in the female generativeorgans, where they play a part already explained. It is a matter of no little significance from an evolutionarypoint of view, that cil-iated cells are morewidely distributed inthe foetus than in thefully developed ani-mal. As would be ex-pected the movementsof cilia are affected bya variety of circum-stances and reagents ;thus, they are quick-ened by bile, acids,alkalies, alcohol, ele-vation of temperatureup to about 40° C,etc. ; retarded by cold, carbonic anhydride, Fkether, chloroform, etc. In some cases theiraction may be arrestedand re-established bytreatment with rea-gents, or it may recommence without such 157.—Nodes of Ranvier and lines of Fromann(Kanvier). A. Intercostal nerve of the mouse,treated with silver nitrate. B. Nerve-fiber fromthe sciatic nerve of a full-grown rabbit. A, nodeof Ranvier ; J/, medullary substance renderedtransparent by the action of glycerin: CY, axis-cylinder presenting the lines of Fromann, whichare very distinct near the node. The lines are lessmarked at a distance from the node. All this 174 COMPARATIVE PHYSIOLOGY. seems to point to ciliary action as falling under the laws gov-erning the movements of protoplasm in general. It is impor-tant to bear in mind that ciliary action may go on in the cellsof a tissue completely isolated from the animal to which it he-longs, and though influenced, as just explained, by the sur-roundings, that the movement is essentially automatic, that is,independent of any special stimulus, in which respect it differsa go
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