146 SPECIAL PHYSIOLOGY. 



into one end of a piece of the intestine of a recently killed animal, the 

 other end being of course tied, and the cavity quite filled with water. 

 It is also shown by the temporary contraction of dead arteries, which, 

 after a time, again relax. 



CILIARY MOTION. 



The presence of cilia on certain so-called ciliated mucous and serous 

 membranes in man, has been mentioned in the account of the ciliated 

 epithelial tissues (p. 67) ; and it has been noticed that ciliated epithe- 

 lium exists on similar membranes of both the warm- and cold-blooded 

 Vertebrata, and in various parts of the bodies of many Mollusca, Mol- 

 luscoida, Annuloida, Coelenterata, and Protozoa. 



Cilia are found in man and other air-breathing Vertebrata, chiefly 

 in the respiratory passages. They occur in man, in what may be 

 called the middle region of the nasal cavities, in the frontal and other 

 sinuses, in the upper part of the pharynx, in the larynx from below 

 the vocal cords, and in the trachea, bronchi, and bronchise, down to 

 the ramifications of the smallest bronchial tubes, but not in the air- 

 cells of the lungs. They are present also in the Eustachian tube and 

 tympanum of the ear, and in the nasal duct and lachrymal sac. They 

 are likewise found on the sides of the ventricles of the brain, and 

 within the central canal of the spinal cord. In the warm-blooded 

 Mammalia, they exist in the same situations as in man. In Birds, 

 they are present likewise in the air-sacs distributed through the trunk 

 of the body. Amongst the cold-blooded Vertebrata, cilia exist, not 

 only in the ordinary situations, but, in Reptiles, in the pericardium, 

 peritoneum, and oesophagus, and also in the uriniferous tubuli, and 

 sometimes in the Malpighian capsules of the kidneys. In the frogs, 



id 



they are found also on the roof of the mouth ; and in the ichthyoid 

 Amphibia, on the gills. In Fishes, the gills are destitute of cilia ; but 

 these exist in the cavity of the nose, and in the respiratory chambers 

 of the amphioxus. In the Mollusca and Molluscoida, cilia are found 

 in the alimentary canal and bile-ducts, and on the gills of both the 

 univalve and bivalve kinds ; also on the respiratory apparatus, when 

 this consists of simple tentacula (hydrozoa), or is reduced to a respi- 

 ratory sac or atrium (timicata). In the Annelida, cilia are commonly 

 found on some part or other of the body ; and in the Annuloida, always 

 in the so-called water-vessels and other parts of the scolecida, and in 

 the* auibulacral tubes of the echinodermata ; also in most aquatic 

 Annelida and Annuloida, on certain parts of the head, probably the 

 seats of an olfactory sense. In the Coelenterata, they are found very 

 largely developed in the bodies of the ciliograde actinozoa (Beroe, 

 &c.), on the ovarian fringes, and in the interior of certain tubes which 

 ramify through the bodies of the medusoid forms. Lastly, in the Pro- 

 tozoa, they are invariably present upon the surface of all infusoria, 

 and in the interior of certain parts of the ramified tubes of the spongia. 

 They exist, moreover, on the embryos of the amphibia, on the ova or 

 embryos of a large number of the non-vertebrated aquatic animals, 

 and on the gemmules of others. Cilia have not been found in insects, 

 Crustacea, myriopoda, or arachnida. 



