Pedagogical Anthropology, Maria Montessori [online e book reader TXT] 📗

in the blood seem to obey a sort of glimmering consciousness when they rush to the encounter of any danger threatening the organism, and ingest microbes or other substances foreign to the blood; and it is also due to a phenomenon that cannot be explained by the physical laws of osmosis, that the erythrocytes or red blood corpuscles and the plasma in the blood never interchange sodium salts for those of potassium; and lastly the cells of each separate gland seem to select from the blood the special substances that are needed for the formation of their specific products: saliva, milk, the pancreatic juice, etc.

Still another manifestation of final cause is the tendency exhibited by each living individual to make a constant struggle for life, a struggle that depends upon a minimum expenditure of force for a maximum realisation of life, thanks to which life multiplies, invades its environment, adapts itself to it, and is transformed.

Another fundamental synthetic characteristic of life is the limitation of form and size that is a fixed and constant factor in the characteristics of each species; the body of the living individual cannot grow indefinitely.

Living creatures do not increase in quantity by the successive accumulation of matter, as is the case with inorganic bodies, but by reproduction, that is, the multiplication of individuals.

Through the phenomenon of reproduction, life has a share in the eternity of matter and of force, that is, in a universal phenomenon. But what distinguishes it is that the individual creatures produced by other living individuals form, each one of them, an indivisible element in which life manifests itself; and this element is morphologically fixed in the limits of its form and size.

The peculiarities which are attributed to the chemical action of protoplasm are of an analytic character, so far as they concern the fundamental characteristics of life. The constant interchange of matter, namely, metabolism, constitutes undoubtedly a phenomenon peculiar to living matter, protoplasm; but protoplasm does not exist apart from living organisms. And what constitutes its chief characteristic is that, when brought into contact with it, inert substances are assimilated, i.e., they become like it, or rather, are transformed into protoplasm; mineral salts such as the nitrates or nitrites of sodium and potassium are transformed in the case of plants into living plasma capable of germinating either into a rose bush or a plane tree or a palm, and inert organic substances such as bread or wine are transformed into human flesh and blood. So that the phenomenon of assimilation outweighs, as a characteristic of life, the molecular chemical action through which it is accomplished. Since metabolism does not occur in nature as a chemical phenomenon, and cannot be produced artificially, but is found only in the matter composing living organisms, it follows that life is the cause of this form of dynamic action, and not that this dynamic action is the cause of life.[4]

Even the latest theory, developed especially by Ludwig in Germany—that protoplasm contains a separate enzyme for each separate function appointed to a particular task—amounts to nothing more than an analysis of the living organism.

The Formation of Multicellular Organisms

We cannot say that the cell is the element of life, because, in an absolute sense, it is not alive; it lives only when it constitutes an individual. Even the brain cells, the muscular fibres, the leucocytes, etc., are cells; but they do not live independently; their life depends upon the living individual that contains them. We may, however, define the cell as the means, the morphological material, out of which all living organisms are formed: because, from the algæ to the orchids, from the cœlenterata up to man, all complex organisms are composed of an accumulation of those microscopic little bodies that we call cells.

The manner of union between the cells in the most primitive living colonies, whether vegetable or animal, is analogous to that followed in the segmentation of the ovum in its ontogenetic (i.e., individual) development.

But the manner of construction differs notably, as between animal and vegetable cells.

Vegetable cells, on the one hand, have a resistant and strongly protective membrane; animal cells, on the contrary, have either a very thin membrane or none at all. Vegetable cells, as though made venturesome by their natural protection, proceed to invade their environment in colonies—in other words, the cells dispose themselves in series of linear ramifications—witness the formation of primitive algæ; and analogously the expansion of the higher types of vegetation into their environment, with branches, leaves, etc. And just as though the vegetable cell acquired self-confidence because it is so well protected, it becomes stationary and strikes its roots into the soil.

To this same fact of cellular protection must be attributed the inferior sensibility and hence the permanent state of obscured consciousness in vegetable life.

This protection against the assaults of environment, and the consequent lack of sensibility, constitute from the outset an inferior stage of evolution.

Animal cells have an entirely different manner of forming themselves into colonies; acting as though they were afraid, they group themselves in the form of a little sphere, enclosing their environment within themselves, instead of reaching out to invade it; and subsequent developments of the animal cell consist in successive and complex invaginations, or formations of layers, one within another—instead of ramifications, after the manner of vegetable cells.

Accordingly, if we advance from that primitive animal type, the volvox, consisting of a simple group of cells arranged spherically, like an elastic rubber ball, to the cœlenterata, we meet with the phenomenon of the first invagination, producing an animal body consisting of two layers of cells and an internal cavity, communicating with the exterior by means of a pore or mouth. The two layers of cells promptly divide their task, the outer layer becoming protective and the inner nutritive; and in consequence of their different functions, the cells themselves alter, the outer layer acquiring a tougher consistency, while the inner remains soft in order to absorb whatever nutriment is brought by the water as it passes through the mouth. In this way, there is a division of labor, such that all the external cells protect not only themselves, but the whole organism; while the internal cells absorb nutriment not only for themselves but for the others. This is the simplest example of a process that becomes more and more complex in the formation of higher organisms; in adapting themselves to their work, the cells become greatly modified (formation of tissues) and perform services that are useful to the entire organism. And at the same time, because of the very fact that they have been differentiated, they become dependent upon the labors of others, for obtaining the means of subsistence. Similar laws seem to persist even at the present day in the formation of social organisms, in human society.

During the development of the embryo, all animals pass through similar phases; and to this man is no exception.