148 SPECIAL PHYSIOLOGY. 



The ciliary motion continues for one, or sometimes for several days 

 after death, in the amphibia and other cold-blooded Vertebrata, as in 

 the turtle, though for a shorter time in the warm-blooded Vertebrata, 

 often ceasing in birds after the lapse of fifteen to thirty minutes. It 

 endures longer, however, in Mammalia, the time varying from two to 

 forty-eight hours ; it lasts longer in warm than in cold weather. The 

 ciliary movement continues for a time on portions of the mucous mem- 

 brane, detached from the body ; and is said to have been observed in 

 the fresh-water mussel even in a state of putrefaction. It is quick- 

 ened by touching the cilia briskly with a foreign body ; also by con- 

 tact with the serum of the blood. Blood preserves the power of move- 

 ment, for cilia immersed in it, exhibit motion at the end of three days, 

 whilst water destroys it in three hours. The blood of the Vertebrata 

 arrests the action of the cilia of the Invertebrata. Light does not 

 affect the motion, nor electricity, unless it be strong enough to destroy, 

 or chemically decompose, the tissue. This curious movement is in- 

 creased in rapidity, and may even be revived by the action of heat: 

 it is diminished by cold ; thus, in warm-blooded animals, it ceases at a 

 temperature of 43, whilst in the frog it continues even at the freezing- 

 point of water. It is retarded by water, and destroyed by various 

 chemical agents, by bile, or even by fresh water, in the case of marine 

 Mollusca; but weak alkaline solutions revive it. The motion is not 

 influenced by narcotics generally, nor yet, it is said, by some poisons 

 which annihilate muscular, contractility ; but prussic acid may affect 

 it, and it is temporarily suspended, like the muscular action of the 

 frog's heart, by the vapor of chloroform. No nerves have been traced 

 to the cilia, nor do they appear to be governed or influenced through 

 the nerves or nervous centres; their motion continues in the frog for 

 days after destruction of the brain ; they exist in animals apparently 

 destitute of nerves ; and, lastly, motion may continue in a single cilium 

 detached, with its epithelial cell, from the rest of the body. Further- 

 more, they have been seen in action in the turtle after the muscles 

 have ceased to exhibit any signs of contractility. 



The true explanation of the phenomenon of ciliary motion has yet 

 to be discovered. By some it has been supposed that the cause of 

 the motion is not intrinsic, but that it is dependent solely upon certain 

 chemical interchanges between their substance and the surrounding 

 medium. The opposite view, that it is due to the action of an animal 

 .substance endowed with a form of vital contractility, seems more 

 probable (Sharpey). No trace of muscular fibres, or fibrillge, has been 

 found at their base; their motion differs most remarkably from mus- 

 cular motion, in not being affected by electricity of moderate intensity, 

 or by certain narcotics, and also in lasting much longer after death. 

 But, on the other hand, no particular structure seems to be essential 

 to the possession of contractility, which is manifested equally in the 

 striated and non-striated fibres, in the simple fibre cells, and, as well 

 known, in other single sarcodous cells, and even in masses of proto- 

 plasm; it is also exhibited in the heart of the embryo chick, where 

 this is composed solely of nucleated cells, having no fibres developed 

 in it. On this point, too, it has been suggested that the cilia may 



