On Jun. 14, 1940, Charles Armstrong and V. H. Haas published Immunity to the Lansing Strain of Poliomyelitis as Revealed by the Protection Test in White Mice in JSTOR. 

Armstrong adapted the Lansing strain of poliomyelitis to cotton rats and then to laboratory mice, thus providing investigators with an inexpensive experimental animal for polio studies. 

This meant that at least one strain of poliovirus was available for research purposes in an animal far less expensive than the monkey.