64 CILIARY MOTION. [CHAP. n. 



the interference of the nervous system ; nor is it likely that a move- 

 ment existing over so extended a surface, as that by the cilia, would, 

 if effected by muscles, be independent of nervous influence. 



Alterations of temperature affect the ciliary motion, owing, doubt- 

 less, to the physical change they induce in the epithelial particles. 

 In warm-blooded animals it ceases on a reduction of the temperature 

 below 43 F. In cold-blooded animals, however, it continues even 

 at 32. In all, a very high temperature effectually puts a stop to it. 

 It is interesting to notice, that all observers agree in stating, that 

 blood is the best preservative of the ciliary motion, but the blood 

 of vertebrata destroys it in the invertebrata. Bile puts a stop to it, 

 very probably by reason of its thick and viscid nature, and not from 

 any chemical influence. 



This phenomenon exists most extensively in the animal kingdom. 

 It has been found in all the vertebrate classes ; and in the inverte- 

 brata likewise, with the exception of the Crustacea, arachnida, and 

 insects. It is the agent by which the remarkable rotation of the 

 embryo in the ova of mollusca is effected ; and it occurs 011 the surface 

 of the ova of polypes and sponges. The bodies of some of the infu- 

 soria are covered with cilia, which are apparently employed by them 

 as organs of locomotion and for the prehension of food (fig. 2, g). 



In man, the ciliary motion has been ascertained to exist on several 

 surfaces : 1. On the surface of the ventricles of the brain and on the 

 choroid plexuses. So delicate are the cells of epithelium here, that 

 the slightest mechanical injury destroys them ; it is, therefore, very 

 difficult to see the movement. Valentin states, that its duration is 

 considerable in these parts, so that it may be seen in subjects used 

 for dissection. 2. On the mucous membrane of the nasal cavities, 

 extending along the roof of the pharynx to its posterior wall, on a 

 level with the atlas, on the upper and posterior part of the soft 

 palate and in the immediate neighbourhood of the Eustachian tube, 

 extending through the tube itself to the cavity of the tympanum. 

 3. On the membrane lining the sinuses of the frontal bone, the 

 sphenoid, and the superior maxillary. 4. On the inner surface of 

 the lacrymal sac and lacrymal canal. 5. On the membrane of the 

 larynx, trachea, and bronchial tubes. 6. On the lining membrane 

 of the female organs of generation. It does not exist in the vagina ; 

 but it may be traced from the lips of the os uteri, through its cavity, 

 and through the Fallopian tubes to their fimbriated margins. 



In nearly all these instances there appears to be a mechanical 

 use for the ciliary movement, namely, to promote the expulsion 

 of the fluid secreted by the surfaces on which the cilia exist. 



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