TISSUES OF THE BODY. 159 



finger \vhich is alternately bent and extended ; (2), the funncl-sliaped 

 (trichterformige), in which the upper portion of the hair describes a circle 

 in swinging, and the whole a cone, whose apex is formed by the firmly 

 attached base of the cilium ; (3), the oscillating, in which the whole hair 

 sways more like a pendulum from side to side ; and (4), the undulating. 

 In this the hair executes a movement like the lash of a whip moderately 

 wielded, or the tail of a spermatozoon. Of all these forms of ciliary 

 motion the first appears to be by far the most frequent (2). 



This movement appears quite independent of the circulatory and 

 nervous systems. Destruction of the latter or interruption of the stream 

 of blood causes no cessation of its activity. The cilia, also, of detached 

 cells persist in their oscillation still, as we have already remarked. 

 Should they, however, become separated from their cells they cease to 

 manifest vitality, and soon disappear completely in the water surrounding 

 them. Ciliary motion, farther, is of longer duration than the life of the 

 animal, but with extraordinary differences. Sometimes it only lasts a 

 short time, especially among birds, and also mammals, where it continues 

 about until the cooling of the corpse, whilst among cold-blooded animals 

 it may be observed for days (3). 



Elevation of temperature increases the energy of this movement, until 

 finally at from 44 to 45 C. coagulation commences. On the other hand, 

 cold has a retarding and finally destructive influence, while agents which 

 do not act chemically do not disturb it in the least. Thus it continues 

 unimpeded in serum, milk, and also in urine. Water accelerates ciliary 

 motion at first, but subsequently puts an end to it rapidly, owing to its 

 action on the very delicate cell. The addition of bile produces an injurious 

 effect on it also, while that of alkalies, acids, alcohol, and such like, put 

 an end to it for ever. A very interesting discovery was made not long 

 since by Virchow, that ciliary motion which has come to a state of 

 rest under normal conditions may be again excited by the application 

 of dilute solutions of soda and potash (4). The influence of gases on 

 the phenomenon has also been lately investigated by Kuhne. It appears 

 that like protoplasmic contractility, to which they are akin, the motions of 

 the cilia require oxygen for their support, and that 'hydrogen causes them 

 to cease. They may be again set agoing by the introduction of a stream 

 of oxygen into the medium in which the cells are immersed. Acidulation 

 also with carbonic acid has a retarding influence on the ciliary motion, 

 counteracted again by alkaline vapours. The retarding effects of alkaline 

 vapours can also be met by acid ones. 



There seems to be an inclination to bring this ciliary motion physiolo- 

 gically to bear upon the transport of small bodies, and to ascribe to it, for 

 instance, the power of forwarding mucus from the nose and lungs, and 

 the ovum from the ovary into the uterus. But these are surely only 

 incidental objects of ciliary motion, which receive their just value when 

 we take into consideration the fact that coatings of ciliary cells occur in 

 completely closed cavities. That the little hair-like appendages may 

 effect a change of locality of the whole body, however, of lower organisms, 

 or induce a motion in the water in contact with the surface of the latter, 

 or, finally, a rotation of alimentary matters in their digestive tract, &c., 

 is beyond doubt. 



REMARKS. 1. The discovery of ciliary motion appears to have been made Ly 

 A. de Heyde, in the year 1683*; and the Dutch Coryphsei of former days were also 

 acquainted with it. But the most accurate studies, dating from 1830, in which this 



