This "baby cage" was marketed for families living in tenements without easy access to outdoor spaces.
Suspended from the side of the building, the baby would have access to fresh air and sunlight through the cage's wire frame, and still have sufficient room to play with toys, according to a patent filed in 1922 by an Emma Read of Spokane, WA. The patent also notes that the cage could double as a place to sleep, with removable curtains working to prevent a draft.
There is an additional photo and further explanation at the Atlantic link.
Link, via. Photo credit Getty Images.