How was Herbert Spencer's view that society was a "social organism" manifested by political and economic principles of the 19th century?
Spencer's view was manifested mainly in the fact that the political and economic principles of the time tended very much towards laissez-faire capitalism.
Spencer viewed society as a social organism that could improve itself or could decline in health. He believed in the ideas that came to be called Social Darwinism and which held that society would improve if the various parts of society became more "fit." Laissez-faire capitalism embodied this idea. It allows for relatively unbridled competition in society. This competition improves society by discovering which people or groups are "fit" and can improve society and which are "unfit" and will hurt society. By finding this out and giving more power and influence to the fit, laissez-faire capitalism is aligned with ideas such as those of Spencer.