TEGUMENTAHY ORGANS. G45 



arranged with their long axes vertical to the surface on which 

 they rest, and have often distinct vibratile cilia at their broad 

 free end. The vibratile cilia of the epithelial cytoblasts, are 

 larger and more extensively distributed in the foetus than in 

 the adult, as shown by Henle on the human epiglottis ; and 

 they are continued vibratile on the epithelium through the 

 larynx, trachea, and the minutest ramifications of the bronchi, 

 and the cells of the lungs, where the ciliated cytoblasts have 

 the usual cylindrical form. 



The epithelial cytoblasts continue cylindrical in the 

 ducts of most glands, in the stomach, and along the whole 

 intestine to the anus, where the epithelium abruptly 

 unites with the flat-celled exterior epidermis, and they 

 have the same cylindrical form in the interior of most of 

 the uro-genital passages. In the female, however, the flat- 

 celled epithelium lines the entire vagina, and the cylin- 

 drical cytoblasts with vibratile cilia, perceptible in the adult 

 state, begin about the middle of the cervix uteri, and con- 

 tinue throughout the body of the uterus and along the 

 Falopian tubes and their fimbriated terminations. The 

 epithelium of serous membranes consists of flat cells, with a 

 distinct central nucleus in each, and arranged in a tesselated 

 form, as seen on the peritoneum, pleura, pericardium, tunica 

 vaginalis testis, synovial membranes, and membranes of the 

 brain. Vibratile cilia are more rarely observed 011 the epi- 

 thelial cytoblasts of serous membranes, and exist on the 

 lining membrane of the ventricles of the brain, and on the 

 exterior peritoneal surface of the fimbriated ends of the Fal- 

 lopian tubes. The epithelial cells detached from the parietes 

 and ducts of secerning tubuli, and from other mucous sur- 

 faces, are observed isolated and mixed, like corpuscles, with 

 the various secretions and excretions, as in mucus, saliva, 

 lachrymal fluid, bile, and urine, and they appear to form the 

 nuclei of morbid irritation, and the corpuscles of morbid 

 secretions, in various pathological states. 



Hairs, bristles, and spines are merely epidermic appen- 

 dages, developed, like teeth, in highly vascular cutaneous sacs 

 or follicles ; they are formed by the successive aggregations of 

 cytoblasts, and are gradually protruded from the piliferous 

 follicles by the growth and elongation of their constituent 

 cytoblasts, and by the addition of new layers to their ex- 



