114 



THE AMERICAN MONTHLY 



[June, 



into the air-vesicle or not. In this case 

 the water is caused to flow over the 

 ciliated surfaces, partially by a respir- 

 atory movement, and partially by the 

 action of the cilia themselves : while, 

 in lower forms (Infusoria and MoUus- 

 ca, e. g.) it is renewed mostly by the 

 latter means. Currents not depend- 

 ent upon cilia are, however, seen in the 

 sponge and in the stem and branches 

 of sertularia, which have no cilia, also 

 as seen in the introcellular movements 

 of fluids in Chara, Vallisneria, hairs of 

 Tradescantia, &c. The cilia upon the 

 outer surface of Infusoria, Polypes and 

 Medusse, as well as on various em- 

 bryos, must be regarded as belonging 

 to the respiratory system. 



Besides acting as true respiratory 

 organs, vibratile cilia act mechanically 

 as a means of clearing the respiratory 

 passages of foreign matter, mucus, 

 dust, &c. The currents being in this 

 connection always in the direction of 

 the external surface (i. e. in the. tra- 

 chea, up : in the nasal passages 

 towards the external meatus, in the 

 frontal and maxillary sinuses towards 

 their respective openings and in the 

 lachrymo-nasal ducts towards the 

 nasal cavities. CI. Bernard experi- 

 mented with a rabbit, by placing its 

 head for some time in a bladder into 

 which air was forced, containing large 

 quantities of charcoal dust. He was 

 unable to find any in the lungs, it 

 being arrested by the cilia of the na- 

 sal passages and trachea. While the 

 cilia undoubtedly act powerfully in 

 this manner, they may at times allow 

 the passage of foreign particles, as is 

 seen in false pigmentation of lungs. 

 This probably happens only when the 

 cilia are overpowered by long con- 

 tinued exposure to dusty air, as in 

 factories and mines. In the Eusta- 

 chian tube the cilia prevent foreign 

 matter from entering the middle ear. 



To the respiratory function we find 

 in Infusoria and Mollusca, (e. g.) 

 added that of prehension of food. 'I'he 

 vibrations of the cilia cause a vortex 

 to be formed in the water, by means 

 of which particles of food in the phy- 



tivorous species, and smaller animal- 

 cules in the carnivorous tribes are 

 brought to the mouth. In Mollusca 

 the cilia may at all times be seen 

 sweeping nutritive particles towards 

 the entrance of the digestive tract. In 

 Infusoria as well as in the Ctenophora 

 and Acalepha, etc., cilia act likewise 

 as locomotor organs, being: in some 

 cases, as we have before remarked, 

 apparently under the control of the 

 will. 



Leaving the respiratory, alimentary, 

 and locomotor functions of vibratile 

 cilia, we find them filling a most im- 

 portant post in the processes of fertil- 

 ization and reproduction. Both in 

 plants and animals we see their con- 

 stant attendance upon the process of 

 fertilization. While in the reproduc- 

 tive organs of animals they render 

 great mechanical aid towards bring- 

 ing the unimpregnated ovule in con- 

 tact with the fertilizing cell. Purkinji 

 and Valentin found the movements in 

 rabbits to be especially brisk in the 

 fallopian tubes, less so in the cornua 

 of the uterus, still less in the conjoined 

 parts, and most lively on the lips of 

 that organ, and of some strength in 

 the vagina. The movement in mam- 

 mals is in the fallopian tubes, towards 

 the uterus, while in the uterus itself 

 it is reversed, being from the cervix 

 toward the fundus. According to Dr. 

 Beck, (Flint's Physiology, p. 890,) at 

 the occurrence of the orgasm in the 

 human female, "the os opens, to the 

 extent of fully an inch, making five or 

 six successive gasps, drawing the ex- 

 ternal OS into the cervix each time, 

 powerfully." Here we see a provi- 

 sion of nature, compensating for the 

 absence of cilia in the human vagina. 

 This action of the os draws the male 

 elements within the cervix when they 

 come in contact with the ciliated epi- 

 thelium, and are carried by its action 

 as well as by their own vibrations, to 

 the fundus of the uterus, when fecund- 

 ation, as a rule, takes place. In other 

 mammals (e.g., rabbits) where the sex- 

 ual approach takes place only at peri- 

 ods of heat or rut, ciliated epithelium 



