Isolated Crowds & People in Crowded Isolation

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There are crowds and then there are crowds, crowds that are big and filled with people, and then crowds that are filled, but somehow strangely not with people even though they are there--large groups of isolated people.  These photos show up now and again, as they did today--I gathered four examples, below.

[Student nurses, Roosevelt Hospital, New York City, 1938. Found at the Pinterest collection of Christian-Paul North, here]

 This image is of a church or social service at Pentonville Prison in 1855. 

Lonely hatted man in a very large crowd on Coney Island, Brooklyn, U.S.A, as captured by Weegee, ca. 1950.   (The Hat Man is at the extreme bottom right corner.)