These cells . . . are independent living beings, the citizens of the state, which constitutes the entire multicellular organism."[1]
Again, he declares: "Every cell is an independent organism. ... It performs all the essential functions which the entire organism accomplishes. Every one of these little beings grows and feeds itself independently. It assimilates juices from without, absorbing them from the surrounding fluid; the naked cells can even take up solid particles at any point of their surface, and therefore eat without using any mouth or stomach. Each separate cell is also able to reproduce itself and increase. The single cell is also able to move and creep about, if it has room for motion, and is not prevented by a solid covering; from its outer surface it sends forth and draws back again finger-like processes, thereby modifying its form. Finally, the young cell has feeling, and is more or less sensitive."[2]
Elsewhere, even more pointedly, he affirms, "The many-celled organism is ordered and constituted on the same principles as the civilized state, in which the several citizens have devoted themselves to various services directed toward common ends."[3]
Both biology and sociology treat of the phenomena of life; both involve psychological as well as merely physical conditions. In the natural order of the sciences the one leads up to the other by an inevitable sequence. There is a similarity in the processes of growth between biological and sociological structures which is noteworthy and most suggestive. Inorganic substances grow by simple accretion, or addition to their bulk. Their growth is involuntary, and is chiefly determined by the operation of external forces and conditions. Organic substances, on the contrary, grow by intussusception a process of waste and repair initiated and carried on in the individual cells or structural units throughout the internal constitution of the organism; and their growth is mainly stimulated by internal, volitional effort. In this respect, as I have elsewhere argued, "the growth of societies resembles that of organic substances; it is a sort of vital chemistry."[4] The individual in his relation to society resembles the cell in its relation to the vegetal or animal organism. The death of individuals, and the birth and growth of others to fill their places in society, proceed in like manner with the processes of waste and repair in organic structures.
In the biological structure, however, the attractive forces which bind atoms into cells and cells into an organic unity are molecular and physical. In the sociological structure they are functional and psychical. And herein, I think, lies the explana-
