Page:Popular Science Monthly Volume 8.djvu/78

68 surface of the body is touched with the point of a pin, or with another body producing a chemical alteration, as for example a small drop of acid, or when a current of electricity is passed through it, the threads are drawn in, and the entire body contracts into the form of a spherical lump. The same threads perform also the function of providing alimentation.

When a small infusorium or any other nutritive particle comes accidentally in contact with the extended pseudopodia, these run quickly over it like a fluid, wind around it with their numerous little branches, fuse into one, and press it into the interior of the body, where all the nutritive portions are rapidly absorbed and immediately assimilated, while all that is useless is quickly ejected.

The variations among the different moners, of which so far sixteen kinds have been described (Haeckel's "Monographie der Moneren)," consist partly in the various forms of the pseudopodia, but especially in the different kinds of propagation. Some of them merely divide into halves on reaching a certain size; others put forth little buds which gradually separate from them; and others experience a sudden division of the mass into numerous small spherical bodies, each of which instantly begins a separate existence and gradually reaches the size of the ancestral organism.

The chemical examination of the homogeneous protoplasmic body shows that it consists throughout of an albuminous or slime-like mass, hence of that azotic carbonate of the character of the highly-compounded connective group called proteine, albuminoids, or plasson bodies. Like other chemical compounds of this group, protoplasm exhibits several reactions which distinguish it from all others. It is easy to detect it under the microscope, on account of the facility with which it combines with certain coloring matters, as carmine and aniline; it is colored dark yellow or yellowish brown by iodine and nitric acid; and it is coagulated by alcohol and mineral acids, as well as by heat. The quantitative composition of protoplasm, though in some cases greatly varying, resembles as a whole that of other albuminoids, and hence consists of from fifty to fifty-five per cent, of carbon, probably six to eight of hydrogen, fifteen to seventeen of nitrogen, twenty to twenty-two of oxygen, and one to two of sulphur. Protoplasm possesses the quality of absorbing water in various quantities, which renders it sometimes extremely soft and nearly liquid, and sometimes hard and firm like leather; but it is usually of a medium degree of density. Its more prominent physical qualities are excitability and contractility, which Kühne and others have made a special subject of investigation.

On examining with the microscope the numerous substances constituting the various organs of the higher animals, it appears that they all consist of a large number of minute elements, known since Schleiden and Schwann (1838) by the name of cells; and in these cells