Silver staining of collagen and reticulin fibres and cerebral capillaries by means of physical development

A method for demonstrating collagen and reticulin fibres and the network of brain capillaries has been worked out on the basis of a new silver staining principle. It may be applied to sections as thick as 200 mu m from both frozen and embedded material. The principle is as follows: the 1,2-glycol groups of tissue elements, including connective tissues, are converted to aldehyde groups by periodic acid. The aldehyde groups form colloidal silver particles in an ammoniated silver nitrate solution of pH 13. At this pH value, however, it is only the connective tissue that can bind the colloidal silver which is being formed. After the silver ions have been washed out of the sections, the silver grains deposited in the connective tissue are finally enlarged to microscopic dimensions by physical development.