Histology; normal and morbid.
- Dunham, Edward K. (Edward Kellogg), 1860-1922
- Date:
- 1898
Licence: Public Domain Mark
Credit: Histology; normal and morbid. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
26/466 page 30
![by the streaming of the cell-body into that protrusion. The fate of the particle thus incorporated dejjends upon its nature. If it be serviceable as food, it is gradually digested and ab- sorbed, or such parts of it as are digestible are so utilized, and the remainder, no longer of use to the amoeba, is extruded from its body. These phenomena reveal powers of perception and selection on the ]>art of this cell which are very closely akin to the intelligence of more complex organisms. They also demonstrate its poAver of assimilating material from without, to serve as nourishment and the source of the energy which it expends in executing its movements and in carrying on the chemical processes pertaining to its internal economy. At intervals, there appears within the endoplasm a small, clear, spherical spot. This gradually increases in size and constitutes a little drop of fluid, sharply defined from the surrounding cytoplasm. After it has attained a certain size, it suddenly disappears, the cyto- plasm around it coalescing and leaving no trace of its existence. Such a clear space, filled with fluid, within the body of a cell is called a vacuole, and those which are suddenly obliterated, contrac- tile vacuoles. Their purpose is not clearly understood, but prob- ably has to do with a primitive circulatory or respiratory function, since contractile vacuoles are not observed in the cells of higher organisms where those functions are carried on by more elaborate mechanisms. Eventually the amoeba reproduces its kind by dividing into two similar cells, eacli of which grows into a likeness to the parent individual. Let us now compare the amoeba with some other varieties of cell, in order to learn what they all have in common. The amoeba has an outer, soft, transparent layer of cytoplasm, the ectoplasm. This is not present in all cells. In many the granular cytoplasm has no envelope, but appears to be quite naked. In other varieties it is enclosed in a distinct membrane. In the great majority of cells the active streaming of the cyto- plasm and the pseudopodial protrusions described in the amoeba are wanting, but the Rrownian movement of the granules is more con- stantly present. The cells have fixed positions and tlieir food is brought to them, usually in solution, so that the more active move- ments so essential to the welfare of the amoeba would be superfluous.](https://iiif.wellcomecollection.org/image/b21223841_0026.jp2/full/800%2C/0/default.jpg)
