Page:Collier's New Encyclopedia v. 02.djvu/49

LEFT BIOLOGY 35 BIOPLAST not absolute. The building material is usually, in part at least, derived from some form of life, save in the case of plants containing chlorophyll which are able by means of light energy to build up complex substances from the simpler, and this power is shared by certain of the bacteria. ^ Certain organisms are able to pass into what is known as latent life, in which all activity ceases, but can be resumed when the environ- ment becomes favorable. This state 13 associated with ^reat reduction of the water content and the resumption of ac- tivity is inaugurated by rapid absorp- tion of water. 6. Relation of tewperature to life. All chemical processes in living matter and in most cases life itself are possible only wiihin certain temperature limits. In a condition of latency, temperatures which are destructive to active life can be withstood. The temperature limits within which active life is possible are somewhat above the freezing point of water and somewhat below the point at which albumen coagulates. In the highly organized mammals the temper- ature limits are narrow and not more than 10° C. The temperature limits for latent life are extremely variable, rang- ing from 3 to 4 degrees above absolute zero to considerably above the boiling point of water, as shown by the spores of certain bacteria. 7. All living matter undergoes cyclic change. All forms of life come from pre-existing forms. The living thing grows until it reaches the form and size characteristic of the species, remains in this stage for a variable and often very short period, then the processes of de- struction overbalance the processes of growth and there is final disruption of structure, or death. The continuation of life is provided for by the separation of parts of the living matter in which again growth overbalances destruction. In some cases this renewal of life is a simple process, in others extremely com- plicated. From this it is evident that the living thing is to be regarded as a most complicated and intricate chemical mechanism whose activity is due to forces acting upon it from without. There is no force inherent in living mat- ter, there are no vital forces independent of and differing from the cosmic forces; the energy manifested by living matter, whatever its form, is counterbalanced by the energy which it receives. It is perfectly true that we cannot explain certain of the forms of energy which the living matter gives off by compari- son with such mechanisms as can be produced, but no other mechanism can be compared in complexity of structure and range of activity with the living thing. Attempts to bridge the difficul- ties of comparison of living activity with mechanisms have been made by the use of such terms as vital force, and there is no objection to the use of such terms provided it be understood that by them we merely express ignorance. Nothing is known of consciousness save as the manifestation of a form of vital activity; nor does it seem to be open to investigation by the methods of science. It is not known whether it is a general attribute of living matter. Nor is any- thing known of the primary origin of life. At some period of the evolution of the earth, hydrogen, oxygen, and car- bon may have come together in such combinations as water and carbonic acid as would give combinations with other substances to form protoplasm. The primary difficulty is to explain the origin of protoplasm; given this, evolution will account for all the forms of life. So far as we know living matter is im- mortal; death is due to the action of conditions which so change its character that the peculiar activities which char- acterize life are no longer possible. It is not inconceivable that ultra-micro- scopic forms of life may be originating at the present time. BION, a Greek pastoral poet, born near Smyrna in the 3d century B. C He appears to have passed the latter part of his life in Sicily. Still extant is his "Lament for Adonis," often imitated by subsequent poets. Besides this there remain of his works only short pieces, many of them fragmentary. BIOPLASM, in biology, a term intro- duced by Prof. L. S. Beale, an English scientist, to designate forming, living, or germinal matter; the living matter of living beings. It is distinguished from formed matter; indeed, the extension of the one and that of the other occur un- der different and often opposite condi- tions. All the organs of the body come from bioplasm. BIOPLAST, in biology, a little nucleus of germinal matter, many of which are scattered through the tissues of the body. It is from these that the growth of new matter proceeds. In the process of heal- ing of a wound near the surface of the body, lymph is poured out, in which may be found bioplasts which have descended from white blood corpuscles. Of these, some produce epithelium, others fibrous connective tissue, unless^ they be too freely nourished, in which case they grow and multiply rapidly, and no kind of tissue whatever results, but pus is alone formed.