Views of the microscopic world : designed for general reading, and as a hand-book for classes in natural science / by John Brocklesby.

  • Brocklesby, John, 1811-1889.
Date:
1851
Catalogue details

Licence: Public Domain Mark

Credit: Views of the microscopic world : designed for general reading, and as a hand-book for classes in natural science / by John Brocklesby. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    length, by tlie aid of which it is alternately extended and shortened. The ani- malcule, at the approach of danger, coils up its tiny cable with the quickness of thought, sinking down towards the spot where it is anchored; and then again when the peril is past, floats upwards in search of food, and swings once more to the utmost extent of its line. This contractile action, as Mantell remarks, is contin- ually going on—now, in one or two individuals only, then in several, and often the whole group suddenly shrinks down into a confused mas^, and the next instant expands, and every little bell becomes fully developed, with its cilia in rapid oscillation. The group in the figure represent a number of animalcules, of this species, in different attitudes and conditions. Some have their stalks stretched to the utmost length, with their crowns of ciha in full action, while others have their stems more or less coiled. Many are single, and others {a a a,) have divided into two, and the stems of several are seen, from which the animalcules have broken and swam away. The length of the body of this species varies from one- two hundred and eightieth of an inch to one-five hundred and seventieth. The self-division of these Infusoria proceeds as follows : The bell first begins to expand in breadth, and then a separation commences extending in the direc- tion of its length, double rows of ciha becoming meanwhile formed. At length, the two parts being perfectly developed, the bell divides into two animalcules, and fringes of ciha next appear encircling the base of each. Soon the young animal- cules twist off from the stem which speedily decays, and after swimming about for some time, at last put forth a new stem from the end of each bell; then fix- ing themselves to some object, they multiply by self-division, and become in their turn the progenitors of a numerous race. In figure 50, two bell-shaped animalcules are seen, which have just been produced from one by separation, each being still attached to the parent-stem by its own stalk. The advantage resulting from the use of a colored fluid, in enabling the observer to detect the stomach-cells of minute Infusoria, has already been mentioned more than once ; but the following detail of its employment by Dr, Mantell, when experimenting upon Bell-shaped Infusoria, is too instructive to be omitted. I place, says this inter- esting writer, a drop of a solution of carmine in the water between the plates of 'glass containing these animalcules; the fluid in which they are floating now appears turbid, and full of gray particles, which are thrown into rapid motion by the vibrations of the ciha, and currents are seen passing to and fro from the mouths of the animalcules. In a few minutes the water gradually becomes clear, and several round spots of carmine are apparent in the body of each animalcule. We have, in fact, caused their little stomachs to be filled with coloring matter, and can now distinguish their number and arrangement. If the body of the animalcule were a mere cavity, it is obvious that the carmine must have collected into a single ball or mass ; but