4 TEE POPULAR SCIENCE MONTHLY. 



Evolution establishes in them both, not differences simply, but defi- 

 nitely-connected differences differences such that each makes the 

 others possible. The parts of an inorganic aggregate are so related 

 that one may change greatly without appreciably affecting the rest. 

 It is otherwise with the parts of an organic aggregate or of a social 

 aggregate. In either of these the changes in the parts are mutually 

 determined, and the changed actions of the parts are mutually depend- 

 ent. In both, too, this mutuality increases as the evolution advances. 

 The lowest type of animal is all stomach, all respiratory surface, all 

 limb. Development of a type having appendages by which to move 

 about or lay hold of food can take place only if these appendages, 

 losing power to absorb nutriment directly from surrounding bodies, 

 are supplied with nutriment by parts which retain the power of ab- 

 sorption. A respiratory surface, to which the circulating fluids are 

 brought to be aerated, can be formed only on condition that the con- 

 comitant loss of ability to supply itself with materials for repair and 

 growth is made good by the development of a structure bringing 

 these materials. So is it in a society. What we call with perfect 

 propriety its organization has a necessary implication of the same kind. 

 While rudimentary, it is all warrior, all hunter, all hut-builder, all 

 tool-maker: every part fulfills for itself all needs. Progress to a 

 stage characterized by a permanent army can go on only as there 

 arise arrangements for supplying that army with food, clothes, and 

 munitions of war, by the rest. If here the population occupies itself 

 solely with agriculture and there with mining if these manufacture 

 goods while those distribute them it must be on condition that, in 

 exchange for a special kind of service rendered by "each part to other 

 parts, these other parts severally give due proportions of their services. 

 This division of labor, first dwelt on by political economists as a 

 social phenomenon, and thereupon recognized by biologists as a phe- 

 nomenon of living bodies, which they called the " physiological divi- 

 sion of labor," is that which in the society, as in the animal, makes it 

 a living whole. Scarcely can I emphasize sufficiently the truth that, 

 in respect of this fundamental trait, a social organism and an indi- 

 vidual organism are entirely alike. When we see that, in a mammal, 

 arresting the lungs quickly brings the heart to a stand ; that if the 

 stomach fails absolutely in its office all other parts by-and-by cease 

 to act ; that paralysis of its limbs entails on the body at large death 

 from want of food or inability to escape ; that loss of even such small 

 organs as the eyes deprives the rest of a service essential to their 

 preservation we cannot but admit that mutual dependence of parts 

 is an essential characteristic. And when, in a society, we see that 

 the workers in iron stop if the miners do not supply materials ; that 

 makers of clothes cannot carry on their business in the absence of 

 those who spin and weave textile fabrics; that the manufacturing 

 community will cease to act unless the food-producing and food-dis- 



