When reconstructing the volumes of organs, or other individual bodies, the areas of these structures are usually determined with the help of serial sections and the volume thus estimated. The actual number of serial sections that have to be taken into account; arranging such a study is of great importance. About 20 equidistant sections are sufficient to determine the volume, even that of extremely irregular formed bodies, whereby the error will not exceed 5%. This technique was used on the brain of Callithrix jacchus and the suprarenal gland of Rana temporaria.