Page:The American Cyclopædia (1879) Volume XIV.djvu/41

 PROTOGENES PROTOPLASM 33 that time. He would assume various shapes to terrify or disgust, and thus drive away his questioner ; but when he found this subterfuge of no avail, he would yield to the demand. PROTOGEXES, a Greek painter, nourished toward the close of the 4th century B. C. He was born at Caunus in Caria, and for 50 years lived unnoticed and poor at Rhodes, until through the intervention of Apelles the Rhodians became aware of his merit. When Demetrius Poliorcetes besieged the city, he was careful not to attack the most defence- less part, because it contained the works of Protogenes. He spent so much time on his works, that Apelles said he never knew when to take his hand off. The " lalysus " was con- sidered his masterpiece, and this when Pliny wrote was preserved in the temple of Peace at Rome. Protogenes was also a statuary, and according to Suidas wrote on art. PROTOPHYTES. See PEOTOZOA. PROTOPLASM (Gr. n-pwrof, first, and TrAdtr^a, form), & term applied to the supposed original substance from which all living beings are de- veloped, and which is the universal concomi- tant of every phenomenon of life. All that is comprehended for brevity under the term life, whether the growth of plants, the flight of birds, or a train of human thought, is thus supposed to be caused by corporeal organs which either themselves consist of protoplasm, or have been developed out of it. Wherever nutrition and propagation, motion and sensa- tion exist, there is as their material basis this substance designated in a general sense as pro- toplasm. The proof of it is held to be fur- nished by the protozoans called moners, the whole completely developed body of which consists solely of protoplasm. They are not only the simplest organisms with which we are acquainted, but also the simplest living be- ings we can conceive of as capable of existing ; and though their entire body is but a single, formless, small lump of protoplasm, and (each molecule of it being like the other) without any combination of parts, yet they perform all the functions which in their entirety con- stitute in the most highly organized animals and plants what is comprehended in the idea of life, namely, sensation and motion, nutri- tion and propagation. By examining these moners we shall gain a clear conception of the nature of protoplasm, and understand the important biological questions connected with the theory. Some moners live in fresh water, and others in the sea. They are as a rule in- visible to the naked eye, but some are as large as the head of a pin and may be distinguished without the aid of a microscope. When com- pletely at rest a moner commonly assumes the shape of a simple sphere. Either the surface of the body is quite smooth, or numerous ex- ceedingly delicate threads radiate from it in all directions. These threads are not perma- nent and constant organs of the slime-like body, but perishable continuations of it, which alternately appear and disappear, and may vary every moment in number, size, and form. For this reason they are called false feet or pseudopodia. Nevertheless, by means of these pseudopodia the moners perform all the func- tions of the higher animals, moving them like real feet either to creep, climb, or swim. By means of these sticky threads they adhere to foreign bodies as with arms, and by shortening or elongating them they drag their own bodies after them. Each thread, like the whole body, is capable of being contracted, and every por- tion of it is as sensitive and excitable as the en- tire form. When any point on the 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 spher- ical lump. The same threads perform also the function of providing alimentation. When a small infusorium or any other nutritive parti- cle comes accidentally in contact with the ex- tended pseudopodia, these run quickly over it like a fluid, wind around it with their numer- ous little branches, fuse into one, and press it into the interior of the body, where all the nu- tritive portions are rapidly absorbed and im- mediately assimilated, while all that is useless is quickly ejected. The variations among the different moners, of which so far 16 kinds have been described (Haeckel's Monographic der Monereri), consist partly in the various forms of the pseudopodia, but especially, in the different kinds of propagation. Some of them merely divide on reaching a certain size into halves ; others put forth little buds which gradually separate from them ; and others ex- perience a sudden division of the mass into numerous small spherical bodies, each of which instantly begins a separate existence and grad- ually reaches the size of the ancestral organ- ism. The chemical examination of the homo- geneous protoplasmic body shows that it con- sists throughout of an albuminous or slime-like mass, hence of that azotic carbonate of the character of the highly compounded connec- tive group called proteine, albuminoids, or plas- son bodies. Like other chemical compounds of this group, protoplasm exhibits several re- actions 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 yellow- ish 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 50 to 55 per cent, of carbon, probably 6 to 8 of hydro- gen, 15 to 17 of nitrogen, 20 to 22 of oxygen, and 1 to 2 of sulphur. Protoplasm possesses the quality of absorbing water in various quan-