Plasma Clot (Watch Glass Technique)
The explant is cultured on the surface of a clot consisting of plasma and chick embryo extract contained in a watch glass, which may or may not be closed with a glass lid, sealed with paraffin wax. This has been the classical standard technique for studying morphogenesis in embryonic organ rudiments and to study the action of hormones, vitamins, carcinogens, etc. in adult mammalian tissues (Figure 2.12).
Since the clot liquefies in the vicinity of explants, they become partly or fully immersed in the medium. Biochemical analyses are not possible because of the complexity of the medium, and the duration of culture is short, usually less than 4 weeks.