Myotube clusters do not bear any quantitative relation to the extent of motoneuron survival.

We conducted a quantitative study of the trochlear motoneurons and the myotube clusters in the corresponding superior oblique muscle of the Japanese quail, before, during, and after the period of normally occurring motoneuron degeneration. A ratio of approximately 1:1 between myotube clusters and neurons was observed at the onset of motoneuron degeneration. The number of myotube clusters prior to neuron death was 37% greater than the number of neurons surviving after cell death. These results are in contradiction with the hypothesis that the number of myotube clusters is the deciding factor for the survival of motoneurons during the critical stages of development.