CHAP. IT.] CILIARY MOTION. 63 



which the brain had been removed, it lasted from four to five days. 

 The longest time they observed it to continue in man and mam- 

 malia was two days ; but in general it did not last nearly so long. 

 What appears to be immediately necessary to the continuation of 

 the movement, is the integrity of the epithelial cells to which the 

 cilia adhere ; for as soon as these shrink up for want of moisture, 

 or become physically altered by chemical reagents or by the pro- 

 gress of putrefaction, the cilia immediately cease to play. 



From these facts we learn two important points in connexion 

 with this phenomenon. The first is, the truly molecular character 

 of the movement. Whatever be the immediate cause of the action 

 of the cilia, it is evidently intimately connected with the minute 

 epithelial particles to which they are attached ; for cilia never exist 

 in man and the higher animals without epithelial particles, and these 

 particles have no organic connexion with the subjacent textures ex- 

 cepting such as may arise from simple adhesion. And, secondly, we 

 perceive, that this movement is independent of both the vascular and 

 the nervous systems, for it will continue to manifest itself for many 

 hours in a single particle isolated from the rest of the system. After 

 death, it remains longer than the contractility of muscle ; a cir- 

 cumstance which, together with the facts just mentioned, indicates 

 that the cilia cannot be moved by little muscles inserted into their 

 bases, as some have supposed. And experiment also shews this 

 independence. If the abdominal aorta be tied, the muscles of the 

 lower extremities will be paralyzed in consequence of their being 

 deprived of their blood ; and on removing the ligature, and allowing 

 the blood to flow, the muscles will recover themselves. But a cili- 

 ated surface is not affected at all in its movements, though the sup- 

 ply of blood to the subjacent tissues be completely cut off. Again, 

 hydrocyanic acid, opium, strychnine, belladonna, substances which 

 exert a powerful effect on the nervous system, produce no influence 

 upon ciliary motion : in the bodies of animals killed by these poisons, 

 the phenomenon is still conspicuous ; and even the local application 

 of them does not hinder it, provided the solutions do not injure the 

 epithelial texture. Shocks of electricity passed through the ciliated 

 parts, do not affect the movement. Lastly, the removal of the brain 

 and spinal cords in frogs, by which all muscular movements are de- 

 stroyed, does not stop the action of the cilia. This striking fact 

 may likewise be adduced to disprove the supposition, that these 

 movements result from the action of minute muscles ; for, although 

 muscles may be excited to contract without nerves, we have no in- 

 stances in the higher animals in which they habitually act without 



