Each worker doing a small part of the overall manufacturing process is known as

There is a manufacturing technique known as Assembly line

In assembly line, each worker are responsible to do small different parts of that whole manufacturing process.

For example : an automobile manufacture company

In this kind of company, usually each worker divided to produce different parts of the automobile , ( some producing the wheel, some producing the engine, etc) then all of the works' result are combined into a complete product

Blood transfusions were rarely done and often fatal; they were outlawed until the nineteenth century.