BIOLOGY (ante), a title under which are classed the sciences that deal with the plus nometta manifested by living matter. It is customary to make a separate group of suck phenomena as pertain especially to mental organization, muter the titles of " psychology" and " sociology," but no natural line can be assigned as separating the snbject•matter under those heads from the more comprehensive term at the head of this article. l'sy cholog,y is closely connected with physidlogy; while there are phases of social life exhibited by animals, as well as men, which come within the province of the biologist, The biological sciences, on the other hand, are distinctly separated from those which treat of non-living 'natter, so far as the properties of living matter distinguish it clearly from all other things,. and Inasmuch as the present state of knowledge.furnishes no link between the living and the non-living.
The distinctive PROPERTIEs OF LIVING MATTER are: 1. Its chemical composition, consisting always of one or more complex forms of a compound of carbon, hydrogen, oxygen, mid nitrogen, the so-called proteine—which has not been found except as:t prod uct of living bodies—joined with a large proportion of water, and forming the chief constituent of a substance which, in its primary state, .is called protoplasm. 2. Its uni rereac disintegration and wwite by oxidation, and its concomitant reintegration, by the intussw ception of new matter. A process of waste following the decomposition of the molecules of the protoplasm, in virtue of which they divide into more highly oxidated products which cease to form any portion of the living body, is a constant phenomenbn of life. It is thought that one of these waste products is carbonic acid, and that the others con tain the remainder of the carbon, nitrogen, hydrogen, and other elements in the compo sition of the protoplasm. The new matter, received to make good this constant loss, is either alreadytformed protoplasmic material, supplied by another living thing. or may be elements of the protoplasm united in simpler. combinations which have constantly to be built into protoplasm by the agency of the living matter itself. In either case the addition of molecules to those already existing is by interposition between the existing molecules, and not at the surface of the living mass. If the processes of disintegration and reconstruction which characterize life balance each other, the size of the living nmss remains stationary; but if the reconstructive process is more rapid than the disintegra tive, the living body is enlarged or grows. However, the increase of size which consti tutes growth is the result of molecular intussusception, and differs front growth by accretion (as may be observed in crystals), which is effected solely by the addition exter nally of new matter; therefore, the term "grow" as applied to stones signifies a process entirely different from "growth" of animals and plants. 3. Its tendency to undergo cyclical dangers. In nature's ordinary course all living matter proceeds from pre-exist ing living matter, some portion of the latter being detached and acquiringa separate and independent existence. The latest forms have the family characteristics of parentage or descent, the same power and process of reproducing the same life, or nearly so, end ing their life after the manner of the parent, and being resolved into more highly oxidated compounds of their elements. A particular living body constantly changes not only its substance, blurt also its form and size, the end of which is the decay and death of that particular body, the continuation of its kind being provided for by the detachment of parts, which pass through the same series of forms as the parent. No forms of non-living matter, not derived from a living source; will exhibit these three properties, nor will they approach to the singular phenomena explained under the above 2d and 3d heads. Living matter has some oth r peculiarities, the principal of which are: the dependence of all its activities upon moisture (and heat within a limited range) and the fact that it usually has a certain structure or organization. As to maistve, there is
a large proportion of water in all living matter; drying to a certain point arrests vital activity, and the entire absence of water is incompatible with either actual or potential life. Still, many of the simple forms may be dried so as to appear to he non-living mat ter while they are yetpotentially alive, and on receiving proper Moisture may return to active existence months or even years after apparent death. Temperature in a proper degree is a necessary condition of life; but more or less heat may destroy life altogether by breaking up the molecular structure on which that life depends. All vital activity, and all the phenomena of mitritive growth, movement, and reproduction are possible only between certain limits of temperature. As the temperature nears these limits the manifestations of life weaken and vanish, though they may recover by a return to nor mal conditions; but any considerable transcending of the natural limits of temperature must result in death. These limits of temperature are not clearly definable, since they vary widely with varying matter, and with the conditions of moisture that accompany temperature. Satisfactory experiments on these points are possible only among the lowest and simplest forms of life; but it has been shown that organisms in a dry state can bear much greater heat than when moist. The spores of fungi in a dry condition have borne 248° to 257' Fah'., but the same spores when moist were killed at 212*. Dry Yeast has borne the surprising temperature of '76* below zero without being killed; and In a.moist condition it has been frozen to 23° without killing; but a lower reduction destroyed life. The resistance of living matter to cold depends greatly on the special form of the matter; hut it should be added that experiments have not been numerous enough to establish definite limits. There are vegetable growths at great. heights in tem perate climates, while in the arctic regions they of show and ice, where the cold is extreme and continues for months together; while the polar seas, north and south, swarm with diatomacm and radiolaria. It is on the diatomocce that all surface life in these regions ultimately depends, and their enormous quantity proves that their rate of multiplication is adequate to meet the demands made upon them, and that it Is not seriously impeded by the low temperature of the water in which they habitually live, a temperature seldom much above freezing. Turning to the maximum of heat that life can endure, we find an equally wide variation. Cohn gives the results of a series of experiments conducted with the view of ascertaining the temperature at which bacteria are destroyed when living in a fluid of definite chemical composition. He made a fluid containing one tenth of a gramme of potassium phosphate, one tenth of a gramme of crystallized magnesium sulphate, one tenth of a gramme of tribasic calcium phosphate, and two tenths of a gramme of ammonium tartrate, dissolved in 20 cubic centimetres of distilled water. If to this fluid a small portion of watercontaining bacteria was added, the multiplication of the bacteria went on rapidly, whether the vessel was open or closed. Such vessels, hermetically scaled, were immersed in water in various temperatures. In those subjected for an hour to 143° Fehr., the bacteria underwent no development, the fluid remaining clear; but at even 122° the fluid became turbid in two or three days in consequence of the multiplication of the bacteria. It is generally believed that the sim pler forms of vegetable life are killed at 140'; but alga live in hot springs at even 208°. Late investigations lead to the conclusion that the immediate cause of the arrest, in the first place, of vitality. and; in the second place, of its destruction. is the coagulation of certain substances In the protoplasm, and that the latter contains various coagulable matters which solidify at certain temperatures.