Spontaneous phagocytosis of boutons on spinal motoneurons during early postnatal development. An electron microscopical study in the cat.

The boutons making synaptic contact with different regions of spinal motoneurons have been studied during the early postnatal period. The observations suggest that a spontaneous glial phagocytosis of boutons of different types occurs mainly during the second postnatal week. This finding is discussed in relation to the previously demonstrated disappearance of boutons from the initial axon segment of spinal motoneurons during the same period of development and also in relation to other degenerative and eliminatory phenomena associated with the normal development of the nervous system.