PROTOPLASM. The most fundamental characteristic of animals and plants is life. While no cme can, as yet, demonstrate just what the physical basis of life is, still there is general agreement that the substance known under the rather indefinite name of protoplasm is that physical basis. The term was first used in 1840 by Purkinje, who applied it to the whole substance of young embryos, so that it included cell walls as well as cell contents. Von Mohl, in 1844, restricted the term to the living con tents of the cell. At present, it is still further restricted, being applied to the living contents of the cell, exclusive of the nucleus, so that the living contents are said to consist of nucleus and protoplasm. In this latter sense, some use the term cytoplasm, instead of protoplasm. Protoplasm is, typically, a viscid substance, usually colorless, and it will not mix with water. In some forms and under some conditions, it has more tenacity and in the resting, but still living condition, found in seeds, it may become as hard as bone. Between the soft, viscid con dition and the bony condition found in seeds like the date and vegetable ivory, there is every conceivable gradation. Chemically, protoplasm consists principally of carbon, hydrogen, nitro gen, sulphur and oxygen, but may contain also smaller quantities of chlorine, phosphorus, po tassium, sodium, magnesium, calcium and iron. Living protoplasm is alkaline, turning the red litmus blue. In regard to the structure, there is great diversity of opinion, but most investi gators believe that it is something like foam or honeycomb. There is a round substance con taining globular bodies of various sizes, so that protoplasm looks like an emulsion, and its gen eral appearance may be simulated by mixing olive oil and common salt. In active living cells, the protoplasm is always in motion and in some cases the motion is so rapid that it can be seen even under a low power of the microscope. In the long cells of the stonewort, Chars, the protoplasm moves round and round in a definite path. In the stamen hairs of the Spider Lily (Tradescantia), the movement is easily observed. Stinging hairs of various
plants will generally show some movement and any very thin leaves of water plants are good subjects. The outer layer of the protoplasm is somewhat different from the rest and has been called the plasmamembrane (the Hautschicht of the Germans). It is sometimes visible and sometimes not, but it is claimed that it is al ways present. The protoplasm of adjacent cells is connected by extremely fine threads, called proto-plasmic connections, which bind the living parts of the plant into a more or less connected whole. These threads pass through almost inconceivably small pores in the cell walls. If the threads are unusually small, they can be demonstrated by using reagents which cause swelling, and then applying dyes to the swollen structures. When plants die and the living contents of the cells dry up and seem to disappear entirely, as in the case of seasoned wood, the threads still remain in the pores and can be demonstrated. There is abundant room for all kinds of investigations upon protoplasm. Consult Butschli, 0., fiber mikroscopische Schiume and das Protoplas ma> ; Wilson, E. B., Cell in Development and Inheritance.> just 75 pounds. Another fragmentary specimen was still larger, and indicated a turtle 14 feet in length. The habitus being robust, this for midable boatman of the Cretaceous seas repre sents the culmination in size of not only the Protostegids, but the entire order. If the paleontologic record may be trusted, not until the comparatively recent Pliocene of the Si walik Hills of Northern India do land species approach in size but scarcely rival the Cre taceous Protostega and Archelon. That, which renders the Protostegids conspicuously interest ing is, however, not so much their size as their structure. It is this group which has gone far towards yielding a convincing solution to one of the most instructive but difficult of all problems presented by reptilians, the origin of Dermochelys, the aleatherbac10 of present day tropic seas.