62 



CILIARY MOTION. 



[CHAP. n. 



Fig. 2. 



posed in rows., and are adapted in their arrangement to the shape 

 and extent of the surface to which they belong ; they adhere to the 

 edges, or to a portion of the surface, of the particles of the epithe- 

 lium, preferring the columnar variety of them. 



During life, and for a certain period after death, these filaments 



exhibit a remarkable move- 

 ment, of a fanning or lash- 

 ing kind, so that each cilium 

 bends rapidly in one direc- 

 tion, and returns again to 

 the quiescent state. The 

 motion, when viewed under 

 a high magnifying power, 

 is singularly beautiful, pre- 

 senting an appearance some- 

 what resembling that of a 

 field of corn agitated by 

 a steady breeze. Any mi- 

 nute objects coming in con- 

 tact with the free extre- 

 mities of the cilia are hur- 

 ried rapidly along in the di- 

 rection of the predominant movement ; one or more blood-discs, 

 accidentally present, will sometimes pass rapidly across the field, 

 propelled in this way, and very minute particles of powdered char- 

 coal may be conveniently used to exhibit this phenomenon, and to 

 indicate the direction of the movement. The action of the cilia 

 produces a current in the surrounding fluid, the direction of which 

 is shewn by the course which the propelled particles take. 



An easy way to observe this phenomenon is to detach by scrap- 

 ing with a knife a few scales of epithelium from the back of the 

 throat of a living frog. These, moistened with water or scrum, 

 will continue to exhibit the movement of their adherent cilia for a 

 very considerable time, provided the piece be kept duly moistened. 

 On one occasion we observed a piece prepared in this way exhibit 

 motion for seventeen hours ; and it would probably have continued 

 doing so for a longer time, had not the moisture around it evapo- 

 rated. However, Purkinje and Valentin have observed it to last 

 for a much longer time than this in connexion with the body of the 

 animal. In the turtle, after death by decapitation, they found it 

 lasted, in the mouth, nine days ; in the trachea and the lungs thir- 

 teen days ; and, in the oesophagus, nineteen days. In frogs, from 



Examples of Cilia : a. Portion of a bar of the gill of the 

 Sea-mussel, Mytilus edulis, shewing cilia at rest and in 

 motion, d. Ciliated epithelium particles from the frog's 

 mouth, e. Ciliated epithelium particle from inner surface 

 of human membrane tympani. /. Ditto, ditto: from the 

 human bronchial mucous membrane, g. Leitcophrys pa- 

 tula, a polygastric infusory animalcule : to shew its surface 

 covered with cilia, and the mouth surrounded by them. 



