CILIATED EPITHELIA L LTRASTRUCTURE 





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Fig. 6. Detail of Fig. 1 showing four basal cells (B). The nuclei (nu) are large and 

 prominent features of these cells with several darker bodies, the nucleoli, the latter a 

 possible indication of mitotic activity. The mitochondria (m) are mostly aggregated 

 beneath the nucleus. The basal cells rest on the basement membrane (BM). The in- 

 tercellular spaces (I) are sometimes the site of lymphocytes (L). Magnification 5,600X 



human trachea. In the efferent ducts of the that they are obviously secretory cells. The 



human testis, the brush cells display an siu'face structures are predominantly of 



elaborate rough-surfaced endoplasmic reticu- brush border type, but resemble more 



lum, a multitude of freely dispersed RNA- those found in the kidney than those 



particles, and a large Golgi zone, indicating of the intestine. IVIoreover, a highly de- 



121 



