An introduction to the study of cytology / by L. Doncaster.

  • Doncaster, L. (Leonard), 1877-1920.
Date:
1920
Catalogue details

Licence: In copyright

Credit: An introduction to the study of cytology / by L. Doncaster. Source: Wellcome Collection.

    28/352 (page 8)
    practically structureless. The first of the three hypotheses is that protoplasm consists of a relatively solid network or reticulum enclosed in a fluid, like a sponge in water; this may be called the reticular hypothesis of Flemming. The second, or alveolar hypothesis, of Butschli, regards the more solid portion as forming a sort of foam, enclosing the fluid in the cavities or alveoli. In thin sections, of course, the alveolar and reticular structures would give similar ap- pearances, but they differ in the fact that in a reticulum the fluid is continuous, while in a foam structure the cavities are closed so that the fluid is divided into a number of separate compartments. The third hypothesis is that of Altmann, which regards the more solid portion as having the form of granules, suspended as in an emulsion in a fluid medium. Each of these three hypotheses is in agree- ment with the facts, in the sense that either reticular, alveolar or granular structure may be obtained in fixed pre- parations of protoplasm, according to the material chosen and the fixative employed. But since each type of structure may be obtained in apparently well-preserved material, there is no satisfactory means of choosing between them, since the structure is too fine for definite results to be ob- tained from an examination of living protoplasm. Under these circumstances the doubt naturally arises whether any of the three represents the real condition as it exists in life, and whether the apparent structures seen in fixed material may not be due to the process of coagulation under the influence of different fixatives. The probability that this is so is greatly increased by the results obtained by Hardy (1899) in the.study of the action of different fixa- tives on a variety of colloidal solutions. Hardy found that when a solution of a colloidal substance is caused to coagu- late, the more solid portion separates from the fluid with