• Bottom-less bath;
  • confocal microscopy;
  • optical sectioning;
  • refractive index mismatch;
  • skeletal muscle;
  • water immersion lens

We describe the design of an organ bath that is of great advantage for microscopy of living specimens, during physiological experiments, or when used in conjunction with confocal microscopy where deep optical sectioning of living specimens is a priority. For the first time water-immersion lenses of the type that may be immersed directly into physiological saline may be used with inverted microscopes. The novel design of the organ bath allows the lens to have direct access to the specimen through a hole in the base of the bath, without requiring a cover-glass. This method is ideal for experiments in which micropipettes or micromanipulators are in use. The benefit of using saline-immersible lenses for optically sectioning deep into living specimens is discussed, with comparison to results with the more commonly used dry, long-working-distance lenses.