Development of the indusium griseum. I. A quantitative light microscopic study of neurons and glia.

A quantitative study of the development of the indusium griseum was carried out in mice. It was not possible to separate the indusium griseum from the cingulate cortex until birth. There was no increase in neuronal numbers between birth and 140 days postnatum, but glial cells probably increased in number from birth to 17 days; 70% of the adult total of glial cells were present at birth. The length of the indusium griseum increased from 1114+/-151 micrometer at birth to 2444+/-54micrometer at 25 days and 2544+/-80 micrometer at 140 days. Although the mean number of cells in equivalent sections decreased with age the distribution of cells was similar at all ages, with the majority of cells lying in the rostral half of the indusium griseum.