The in situ staining of muscles during development with the cholinesterase technique

Developing muscles from forelegs of 11- to 18-day-old mouse embryos were stained in situ for cholinesterase with the copper-ferrocyanide technique. The skin of the legs represents a diffusion barrier for the incubation medium. Therefore, in older embryos the skin was mechanically removed after trypsin digestion. In younger embryos the skin remained on the forelegs after trypsin treatment. With this technique it is possible to follow the establishment of the muscular pattern in the legs.