Neural induction tissue interactions

It has been shown that the type of neural structures induced by the neuralizing factor depends on secondary interactions. The neuralizing factor alone induces foreheads. Mixtures of neuralizing and vegetalizing factors induce hindbrain with ear vesicles or neural tube, depending on the ratio in which the two factors are applied (Toivonen and Saxen, 1955 Saxen and Toivonen, 1961 Tiedemann and Tiedemann, 1964). The modification of the induction response is probably not exerted by the vegetalizing factor itself but by the mesoderm which is induced along with the neural tissue (Toivonen and Saxen, 1968). 

The somites are an intriguing invention of vertebrate embryos. They represent the most overtly segmented structures of the body plan, but they give rise to both obviously segmental (e.g., the axial skeleton) as well as not-so-obviously metameric (dermis and skeletal muscle) elements. In addition, they play a key role in controlling several aspects of the organization of the central and peripheral nervous system of the trunk and participate in several different types of inductive interactions, both within themselves and with neighboring tissues, like the neural tube, the notochord, the metanephric and lateral plate mesoderm, and the ectoderm and endoderm see [1,2] for reviews). 

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