...
Note that Cargille Type 37 is optimal for use at 37 degrees 37ºC but introduces spherical aberrations when imaging beyond anout 10 microns into about 10 μm in aqueous media because it is not refractive indexed matched to water. Zeiss Immersol W in combination with the 60x WI lens might be a better choice in this case , but its RI is corrected for use at room temperature and won't be correct at 37 degrees.
...