We now picture to ourselves the complex living being, animal or plant, with its configuration which distinguishes it from every other being, just as a populous city is distinguished by a thousand characteristics from its neighbour. The elements of this city are independent and autonomous for the same reason as the anatomical elements of the organism. Both have in themselves the means of life, which they neither borrow nor take from their neighbours nor from the whole. All these inhabitants live in the same way, are nourished and breathe in the same manner, all possessing the same general faculties, those of man; but each has besides, his profession, his trade, his aptitudes, his talents, by which he contributes to social life, and by which in his turn he depends on it. Professional men, the mason, the baker, the butcher, the manufacturer, the artist, carry out different tasks and furnish different products, the more varied, the more numerous and the more differentiated, in proportion as the social state has reached a higher degree of perfection. The living being, animal or plant, is a city of this kind.
Law of the Constitution of Organisms.—Such is the complex animal. It is organized like the city. But the higher law of this city is that the conditions of the elementary or individual life of all the anatomical citizens are respected, the conditions being the same for all. Food, air, and light must be brought everywhere to each sedentary element; the waste must be carried off in discharges which will free the whole from the inconvenience or the danger of such debris; and that is why we have the different forms of apparatus in the circulatory, respiratory, and excretory economy. The organization of the whole is therefore dominated by the necessities of cellular life. This is expressed in the law of the constitution of organisms formulated by Claude Bernard. The organic edifice is made up of apparatus and organs, which furnish to each anatomical element the necessary conditions and materials for the maintenance of life and the exercise of its activity. We now understand what is the life, and at the same time what is the death, of a complex being. The life of the complex animal, of the metazoon, is of two degrees; at the foundation, the activity proper to each cell, elementary life, cellular life; above, the forms of activity resulting from the association of the cells, the life of the whole, the sum or rather the complex of elementary partial lives. There is a solidarity between them produced by the nervous system, by the community of the general circulatory, respiratory apparatus, etc., and by the free communication and mixture of the liquids which constitute the media of culture for each cell. We shall have an opportunity of recurring to current ideas as to the morphological constitution of organisms.
CHAPTER III.
THE CHEMICAL UNITY OF LIVING BEINGS.
The varieties and essential unity of the protoplasm—Its affinity for oxygen—The chemical composition of protoplasm—Its characteristic substances.—§ 1. The different categories of albuminoid substances—Nucleo-proteids—Albumins and histones—Nucleins.—§ 2. Constitution of nucleins.—§ 3. Constitution of histones and albumins—Schultzenberger’s analysis of albumin—Kossol’s analysis—The hexonic nucleus.
The chemical unity of living beings corresponds to their morphological unity.
The Varieties and Essential Unity of the Protoplasm.—One essential feature of the living being is that it is composed of matter peculiar to it, which is called living matter, or protoplasm. But this is a somewhat incorrect way of expressing the facts. There is no unique living matter, no single protoplasm; their number is infinite, there are as many as there are distinct individuals. However like one man may be to another, we are compelled to admit that they differ according to the substance of which they are constituted. That of the first offers a certain characteristic personal to the first, and found in all his anatomical elements; similarly for the second. With Le Dantec we shall say that the chemical substance of Primus is not only of the substance of man, but in all parts of his body and in all his constituent cells it is the exclusive substance of Primus; and, in the same way, the living matter of another individual Secundus will carry everywhere his personal impress, which differs from that of Primus.
But it is none the less true that this absolute specificity is based with certainty only on differences which from the chemical point of view are exceedingly slight. All these protoplasms have a very analogous composition. And, if we regard as negligible the smallest individual, specific, generic, or ordinal variations we may then speak in a general manner of protoplasm or living matter.
Experiment shows us, in fact, that the real living substance—apart from the products it manufactures and can retain or reject—is in every cell tolerably similar to itself. The fundamental chemical resemblance of all protoplasms is certain, and thus we may speak of their typical composition. We may sum up the work of physiological chemistry for the last three quarters of a century by affirming that it has established the chemical unity of all living beings—that is to say, a very notable analogy in the composition of their protoplasm.
This living matter is essentially a mixture of the proteid or albuminoid substances, to which may be added other categories of immediate principles, such as carbohydrates and fatty matters. But the latter are of secondary importance. The essential element is the proteid substance. The most skilful chemists have tried for more than half a century to discover its composition. Only during the last few years—thanks to the researches of Kossel, the German chemist, following on those of Schultzenberger and Miescher—we are beginning to know the outer walls or the framework of the albuminoid molecule; in other words, its chemical nucleus.
Physical Characters of Protoplasm.—About 1860 Ch. Robin thought that he had defined living matter sufficiently—or, at least, as perfectly as could be expected at that time—by attributing to it three physical characteristics. They were:—Absence of homogeneity, molecular symmetry, and the association of three orders of immediate principles—albuminoids, carbohydrates and fats. These characteristics assist, but do not suffice, to define the organization.