"The term division of labor has, from long usage, become associated in the public mind with manual processes. But productive labor is, in general, both manual and mental and just as there may be division of manual labor so there may be division of mental labor or division of thought. Modern productive methods tend constantly to separate mental labor from manual labor and then to subdivide each into smaller and smaller parts. The subdivision of manual labor is greatly furthered, as has been seen, by the extended use of tools. Subdivision of mental labor on the other hand is hastened by an increase in the amount of knowledge and mental development necessary to successfully perform the work in hand. Thus the mental labor of designing machinery is performed largely apart from the actual production; and this mental labor has become very closely specialized as the scientific basis of engineering has grown. This process of subdivision is greatly hastened in both manual and mental operations by increased quantity since this, of itself, enables the manager to avail himself of the inherent advantages of division of labor already discussed."

“Specialization, as has been noted, is the confining of human activity to a limited field. In industrial work this means the limitation of an enterprise to a portion of the field and to the production of a limited line of products. But even when the line of products is limited, there are usually many types that are possible in that line and an infinite number of sizes of any one type. Thus suppose a manufacturer specializes in the manufacture of men's shoes. Here there is no limit to the types that may be produced and no limit to the number of sizes of any type since no two feet are exactly alike. Again a manufacturer may specialize on the production of motors between the sizes, say, of one-half horse-power and twenty horse-power. Here again many types are possible and an infinite number of sizes for each type. But it has been shown that one of the essentials of cheap production is quantity, and for a given total output the greatest number of each element entering into the product is secured when the numbers of types and sizes are a minimum.”

“The underlying principle of specialization is division of labor; but the term division of labor has become associated with the individual worker, whereas specialization is, in general, far reaching in its effects, and influences industrial enterprises of all kinds.”

“By standardization is meant the reduction of any one line to fixed types and sizes. Thus in the case of the manufacturer of shoes he selects a few types that, in his opinion, will find favor in the market. But each foot is not measured and a shoe of the required type made to these measurements. A limited number of sizes of each type is manufactured, these sizes being selected, by previous experience, so that any average man can find a pair that will fit him. The same holds true for the case of electric motors discussed above, and in fact for the entire field of manufactured products.”

“The new industrial methods have greatly accelerated certain tendencies that had already manifested themselves in the old domestic factories and some of these deserve more than passing notice as they are affecting not only productive processes but our social organization as well. Perhaps the most important of these influences are those that tend toward”

“There is another and very important ground for standardization and that is the desirability of having parts interchangeable. Standards of exchange have long been in general use, and these have, most usually, been fixed with a view to convenient use rather than on a scientific basis. The units of weight and measure are examples of this form of standard. They may not even be the most logical, or most convenient, but once established they can, in general, be changed only by slow degrees, if at all.”

“It is human experience that as a man concentrates his efforts, either mental or manual, his skill in his chosen specialty, and the quantity of his product increase. It was shown... that specialization in machinery had a powerful influence in specializing the workman and thereby extending the principle of division of labor. But division of labor may be furthered by other influences. The very growth of all lines of human knowledge and activity makes it increasingly difficult for one man to retain a grasp of any one entire field. He must be content to cultivate a small portion of it.”