_The Solidarity of the Anatomical Elements._—The cause of the mortal process—_i.e._, of the extension and the propagation of an initial destruction—is therefore to be found in the solidarity of the parts of the organism. The closer it is the greater do the chances of destruction become, for the accident which has happened to one will by repercussions affect the others. Now the solidarity of the parts of the organism may be carried out in two ways; there is a _humoral solidarity_ and a _nervous solidarity_. _Humoral Solidarity._—Humoral solidarity is realized by the mixture of humours. All the liquids of the organism which have lodged in the interstices of the elements and which soak the tissues, are in contact and in relation of exchange one with another, and through the permeable wall of the small vessels they are in relation with the blood and the lymph. All the liquid atmospheres which surround the cells and form their ambient medium have intercommunication. A change having taken place in one cellular group, and therefore in the corresponding liquid, modifies the medium of the further or nearer groups, and therefore these groups themselves. _Nervous Solidarity._—But the real instrument of the solidarity of the part is the nervous system. Thanks to it in the living machine the component activities of the cellular multitude restrain and control one another. Nervous solidarity makes of the complex being not a mob of cells, but a connected system, an individual in which the parts are subordinated to the whole and the whole to the parts; in which the social organism has its rights just as the individual has his rights. The whole secret of the vital functional activity of the complex being is contained in these two factors:—the independence and the subordination of the elementary lives. General life is the harmony of the elementary lives, their symphony.