Brain abscess, fully developed connective tissue capsule: This is a special stain (Azocarmine) to demonstrate the extent of fibrous connective tissue formation in a well-developed capsule of a brain abscess several weeks of age. The blue-black tissue is collagen. Unlike infarcts, in which fibroblasts do not play a significant role in the reactive changes, there is a vigorous response of fibroblasts in the tissue surrounding a brain abscess. A low-grade fibrous glial scar is formed by astrocytes outside of the connective tissue capsule but this process is far less significant than the collagen production.