Kirkes' handbook of physiology / revised by Frederick C. Busch.

  • Kirkes, William Senhouse, 1823-1864.
Date:
1904
Catalogue details

Licence: In copyright

Credit: Kirkes' handbook of physiology / revised by Frederick C. Busch. Source: Wellcome Collection.

    30/894
    Corti’s demonstration of the rotation of the cell sap in eharacese, and in the earlier part of the century by Meyer in Vallisneria, 1827; liobert Brown, 1831, in “ Staminal Hairs of Tradescantia.” Then came Du jar- din’s description of the granular streaming in the pseudopodia of Khizo- pods and movement in other cells of animal protoplasm (Planarian eggs, v. Siebold, 1841; colorless blood-corpuscles, Wharton Jones, 1840). 2. The Power of Response to Stimuli, or Irritability.—Although the movements of the amoeba have been described above as spontaneous, yet they may be increased under the action of external agencies which excite them and are therefore called stimuli, and if the movement has ceased for the time,-as is the case if the temperature is lowered beyond a certain point, movement may be set up by raising the temperature. Again, contact with foreign bodies, gentle pressure, certain salts, and electricity, produce or increase the movement in the amoeba. The pro- toplasm is, therefore, sensitive or irritable to stimuli, and shows its irri- tability by movement or contraction of its mass. The effects of some of these stimuli may be thus further detailed:— a. Changes of Temperature.—Moderate heat acts as a stimulant; the movement stops below 0° C. (32° F.), and above 40° C. (104° F.); be- tween these two points the movements increase in activity; the optimum temperature is about 37° to 38° C. Exposure to a temperature even below 0° C. stops the movement of protoplasm, but does not prevent its reappearance if the temperature is raised; on the other hand, prolonged exposure to a temperature of over 40° C. altogether kills the protoplasm and causes it to enter into a condition of coagulation or heat rigor. b. Mechanical Stimuli.—When gently squeezed between a cover and object-glass under proper conditions, a colorless blood-corpuscle is stim- ulated to active amoeboid movement. c. Nerve Influence.—By stimulation of the nerves of the frog’s cornea, contraction of certain of its branched cells has been produced. cl. Chemical Stimuli.—Water generally stops amoeboid movement, and by imbibition causes great swelling and finally bursting of the cells. In some cases, however (myxomycetes), protoplasm can be almost en- tirely dried up, but remains capable of renewing its movements when again moistened. Dilute salt-solution and many dilute acids and alka- lies stimulate the movements temporarily. Strong acids or alkalies permanently stop the movements; ether, chloroform, veratria, and qui- nine also stop it for a time. Movement is suspended in an atmosphere of hydrogen or carbonic acid and resumed on the admission of air or oxygen, but complete with- drawal of oxygen will after a time kill the protoplasm. e. Electrical.—Weak currents stimulate the movement, while strong currents cause the cells to assume a spherical form and to become motionless.