558 THE POPULAR SCIENCE MONTHLY. 



produce crystals or not, are formed by a symmetrical aggregation of 

 atoms. The latter are arranged in equilibrium in two directions, per- 

 pendicular to each other, one parallel to the axis of grouping, and the 

 other at right angles to that axis, so as always to compose a symmetri- 

 cal figure. The most complicated bodies, so soon as they are brought 

 under the law of definite proportions, and compose chemical species, 

 are made up of molecules in which the atoms are grouped in prisms, 

 in pyramids, in a word, in polyhedra more or less many-sided, but 

 always of perfect regularity ; so that, in this case, the differentiation 

 is regulated with marvellous harmony. 



We must now rise another degree, and pass from inorganic matter 

 to living matter. What is it that distinguishes the latter from the 

 former ? When we make the answer depend on the results of direct 

 experiment, nothing is easier than to establish the differential charac- 

 teristics of living matter. In the first place, it is organized, that is, 

 the anatomical elements, instead of being homogeneous and symmetri- 

 cal in all points of their mass, are composed by the association of a 

 certain number of different substances, in which carbon predominates, 

 and which are termed immediate organic principles. Then these ele- 

 ments grow. At no time the same throughout, as to the substance 

 which makes them up, they are in a state of unceasing molecular 

 renewal, of constant metamorphosis, of simultaneous and continu- 

 ous assimilation and disassimilation. Besides, the various proper- 

 ties these elements may exhibit, contractility, neurility, and so on, 

 are, in consequence of the growing state that characterizes them, in 

 so unstable a condition of equilibrium that the slightest variation in 

 the surrounding medium is enough to occasion some change in the ex- 

 pression of their activity ; in other words, they have excessive excita- 

 bility and irritability. Such, at least, is the region within which 

 physiology is limited ; but the fact which it does not clearly enough 

 bring out, yet the thing which is the distinctive mark of life, is the 

 harmonious seeking for each other of all these vital monads, the dis- 

 position of biological energies to compose groups of which the end 

 and the reason are found in what we call the individual. The differ- 

 entiations of inorganic matter occur in molecules that are specific, in 

 whatever bulk they are regarded. The differentiations of living mat- 

 ter take place only in individuals whose build and proportions are 

 strictly determined. An iron bar, an iron crystal, and iron-dust, are 

 all still iron. An organic substance fitted for life is nothing, when- 

 ever deprived of connection with an organism. It can display energy, 

 can act ; in a word, can be, so far as to be a living substance, only in 

 virtue of taking place and rank in a certain whole, and assuming cer- 

 tain dependencies and connections with other more or less analogous 

 substances. By itself it is not distinguished in essence from dead 

 matter. It is raised to the rank and clothed with the dignity of life 

 only from the time of its reception into that gathering of which the 



