GROW. 312 GROWTH. admitted to the bar in 1847. Four years later lie was elected to Cuiigress from Pennsylvania and continued to be a member of that body until 18G3; the first half of the time as a Free Soil Democrat, the last as a Republican. From July 4, 1861, to March 3, 1863, he was Speaker of the House of Representatives. He was president of the International and Great Northern Rail- way from 1871 until 1876, a position which made it necessary for him to live in Texas. In the latter year, however, he returned to Penn- sylvania. He declined the Russian mission in 1879, and since 1804 has been Congressman at large from his State. GROWTH (from grow, AS. {irowan, Icel. grOa, OHG. gruoan ; connected with AS. grcenc, Ger. griin, Eng. green ; cf . also Icel. gropr, grCpi, growth). Increase in size or volume. It is not to be confounded with development, which fol- lows or accompanies growth and has to do with the unequal growth of parts of the organism, in- volving an increasing unlikeness of the different parts, i.e. a differentiation or specialization of the body. Hence developnient is the formation of a complex from what was originally a simple whole, as seen in the development of the flower or the chick, which both grow and unfold or develop. Inorganic Growth. Growth, whether that of minerals, of our earth, the solar system, or even of the universe, is primarily due to the action of cosmic energy and of motion. Our solar system, the fixed stars and planets, have had a history, have grown, have developed. Geological history is a process of growth : the continents may be said to have gradually grown to their present size and shape. This is illustrated by the growth or simple increase in size of mineral or inorganic bodies. Crystals, under favornMe conditions, grow by the addition of particles to the outside. There is a certain limit to their growth, and crystals are of different sizes — they take on a definite shape, related to the physical and chemical characters of the mineral sub- stance. Verworn, however, thinks the contrast made between the crystal and the organism is 'unfortunate.' He states that "as regards its physical characteristics the living substance of organisms in its essentials ought to be com- pared with a liquid," and he goes on to state that "liquids grow by intussusception, i.e. if a soluble body be added to a liquid, e.g. salt to water, the latter dissolves the former and stores the mole- cules of the soluble body by diffusion between its own molecules, that is, there is here exactly the same process as in the growth of the organism."' All this goes to show that growth or increase in size, together with some degree of development up to a certain stage (certainly not up to the cessa- tion of power of reproduction), takes place in the inorganic world. Organic Growth. As living beings funda- mentally differ from mineral bodies, so growth in plants and animals is inherently different. Even organic growth is defined as increase in volume, but this does not go far enough. Living organisms are compounds or proteids of mineral matter, forming protoplasm, and they grow by adding to the substances forming their bodies similar substances or food, which is taken within the body by interstitial deposit (intussusception), and these are digested and assimilated. This causes an increase in the volume or bulk of the body. Organic growth is fundamentally a phys- ico-chemical process plus a form of constructive energy which we are unable to comprehend. In our present ignorance we invoke vital force, 'growth force,' or 'bathmism,' words which do dot help us to understand what is behind the plienomenon of increase in volume. Besides sim- ple increase in bulk, there is, as Ryder states, a process of rearrangement, further subdivision of and addition to the material basis of the organ- ism. Growth, also, according to Ryder, pro- ceeds everywliere by "adding to its substance at a rate which corresponds exactly with the rate at which the cube of the dimensions of the grow- ing body is everywhere being increased. All growth is accompanied by movement, for as a cell increases in volume it becomes expanded." "Hence," says Verworn, "growth-movements are common to all living substance, but they take place so slowly that they can scarcely be followed with the eye." That the phenomena of growth are powerful sources of energy is exemplified by the well-known fact that trees growing out of crevices in the rock are able by their roots to force apart huge masses of stone. See Mechanics of DEVELOrMENT. CORHELATION OF THE VOLUMES AND SURFACES OF Organisms. It has been pointed out by I^uck- art and by Herbert Spencer that as organized unicellular bodies increase in bulk, their sur- faces become proportionately less, and that this elementary rule of growth very probaldy leads to the necessity for segmentation or subdivision of the original cellular body, "owing to the un- favorable conditions which continuous growtli establishes between the organism and its sur- roundings, thus developing unfavorable conditions for nutrition, respiration, and consequently for metabolism and growth in general." (Ryder.) But, as Ryder claims, there are "supplementary b'lt equally important principles connected with the c/rometrical ratios with which the forces of growth, reproduction, and metabolism are simul- taneously operative during the development, growth, and evolution of organic types"; and he claims that "without resort to another tvpe or set of adjustments which living beings have effected in relation to the outer world, the pres- ent development of organized resistance, and even of animal motion and mentality, would in all probability have been an impossibility." The primary form of living beings, as the low- est plants and animals, is that of a sphere, the spherical shape being due to gravity and surface- tension. But Ryder" points out that this shape is one "which is itself unfavorable for growth, with a proportionate and concomitant acquisition of new surface, since of all forms of bodies it is the very one which can contain the greatest amount of matter within the least amount of surface." Hence any departure from this primitive spheri- cal form "will increase the proportional amount of enveloping surface in respect to the volume of enveloped matter." Hence, first, the tendency of organs to extend indefinitely in the form of a cylinder, with rounded or hemispherical ends, which becomes more and more attenuated as its length is increased, as in the nerves, or blood- vessels: and. secondly, the formation of flattened disk-like bodies, such as the blood-corpuscles. Why do the nerves, blood-vessels, etc., grow slender and branched? Ryder answers this ques-
