. An elementary course of practical zoology. Zoology. no THE FROG chap. accurately, like the blades of grass in a field when acted upon by a strong wind. If you happen to get under the microscope a good-sized bit of mucous membrane with the cells in position, you will see tha,t the cilia produce a strong current by which small particles are swept along, while detached cells swim about, like little independent animals, by the action of their own cilia. These ciliated epithelial cells, like the columnar cells previously described, are made of protoplasm and each contains a nucleus with one or tw
. An elementary course of practical zoology. Zoology. no THE FROG chap. accurately, like the blades of grass in a field when acted upon by a strong wind. If you happen to get under the microscope a good-sized bit of mucous membrane with the cells in position, you will see tha,t the cilia produce a strong current by which small particles are swept along, while detached cells swim about, like little independent animals, by the action of their own cilia. These ciliated epithelial cells, like the columnar cells previously described, are made of protoplasm and each contains a nucleus with one or two nucleoli clearly brought into view by staining. The action of the cilia can be demonstrated, on a large scale, by placing a freshly-killed frog on its back, turning back or cutting away the lower jaw, and placing a very small cube of cork on the roof of the mouth near to the projection due to the eyes. The cork will be slowly swept back towards the throat. Squamous or Pavement Epithelium.—By scraping the outer surface of a piece of skin with a sharp knife, and examining the scrapings in a drop of water, after staining them, the superficial layer of the skin will be found to be made up of flattened, roughly hexagonal plates (Fig. 30 and Fig. 27, C, U) set closely to- FlG. 30.—Squamous epithelial cells i*i 1 -i from the frog's skin. nu. nuclei. gather, like the tlleS of a mosaic pavement. Each plate has a_ nucleus, and, from its flattened form, is distinguished as a squamous or scale-like epithelial cell. Meaning of the word " Cell,"—We see thus that the body of the frog is partly made up of -distinct elements, which, under a considerable diversity of form, exhibit the same essential structure. Each consists of a mass of living proto-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Park
Size: 1830px × 1365px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1900
