Changes in neural cell pattern induced by the notochord and 
floor plate. Micrograph shows the change in pattern of floor 
plate and motor neuron cell differentiation in response to a 
grafted notochord in chick embryos. In this section of an em- 
bryonic chick spinal cord, the left side shows a normal ventral 
motor neuron pool, labeled with a monoclonal antibody. A 
grafted notochord adjacent to the right side of the spinal cord 
induces an additional floor plate and ectopic motor neurons in 
dorsal regions. 
Research of Thomas M. Jessell. 
