was forth with greatly expanded"; and further on it is said "that the truth thus found to be all-embracing in Biology returns to Sociology ready to be for it, too, an all-embracing truth." Here it is manifest that the two sciences are regarded as yielding mutual elucidations; and if, as the first sentence taken alone may appear to imply, I regard the analogy as showing that Sociology must be based on Biology, then, on the strength of the subsequent sentences, it may just as truly be said that I base Biology upon Sociology. Clearly, when taken together, these passages show the thought to be that for distinct understanding of either science certain conceptions furnished by the other must be possessed. It can not be said that each science is based on the other. Hence the alleged connection must be not a necessary dependence but an exchange of enlightenments. There is direct proof of this. The sociological division of labor had been recognized long before Biology had assumed a scientific form; and "the physiological division of labor," though not thus named, had been long recognized in living bodies as a co-operation among the various organs. In either science the conception might gradually have been elaborated to the full without aid from the other, though with nothing like the same rapidity and clearness.
Let as pass finally to the exposition of the analogy contained in Part II of The Principles of Sociology. It is there said that "between a society and anything else, the only conceivable resemblance must be one due to parallelism of principle in the arrangement of components." (§ 213.) It is shown "how the combined actions of mutually-dependent parts constitute life of the whole, and how there hence results a parallelism between social life and animal life." (§ 218.) Mutual dependence of parts being thus regarded as the essential trait in either case, there is subsequently pointed out a fundamental contrast between the modes in which this mutual dependence is effected in individual bodies and in bodies politic. § 221 begins—
"Though coherence among its parts is a prerequisite to that co-operation by which the life of an individual organism is carried on; and though the members of a social organism, not forming a concrete whole, can not maintain co-operation by means of physical influences directly propagated from part to part; yet they can and do maintain co-operation by another agency. Not in contact, they nevertheless affect one another through intervening spaces, both by emotional language and by the language, oral and written, of the intellect."
It is argued that mutual dependence of parts requires the conveyance of impulses from part to part, and that while "this requisite is fulfilled in living bodies by molecular waves," "it is fulfilled in societies by the signs of feelings and thoughts, conveyed from person to person."
