ABSTRACT
We stressed in Chapter 1 the importance of estimating the volume of the reference space for stereological studies in biomedical applications. Here we describe the most commonly used stereological method for estimating reference volume, the Cavalieri method (Cavalieri, 1635; Gundersen and Jensen, 1987). Other methods that maybe suitable include simple weighing and water immersion. If an organ is of constant and known density then weighing gives a direct method of estimating volume. Volumetry using water immersion relies upon the Archimedean principle of fluid displacement. For large organs such as livers and lungs the method developed by Scherle should be adopted (Scherle, 1970; Weibel, 1979). One problem with water immersion volumetry is that if the object has internal cavities that are open to the outside (such as lung), then when the organ is immersed the cavities fill with water, leading to an underestimate of volume. Therefore, before immersion, the holes in the organ need to be plugged in a watertight manner. For objects that are completely enclosed within another object or matrix, for example the hippocampus within the brain, then water displacement is not feasible.
