Development of visual callosal projection in the microphthalmic stain of mice 944.

The strain of mice 944 produces a recessive microphthalmy. The microphthalmic mice were compared with phenotypically healthy animals of the same litter and with 944-mice bilaterally enucleated at 1. postnatal day (pd). Comparison was done at the 5., 10., 15. and 20. pd after lesion of the right visual cortex 24 hours before. Therefore Nissl- and Fink-Heimer-series were prepared. The results are the following: At 20. pd microphthalmic mice show both retrograde and anterograde degeneration after lesion. Enucleated and control mice produce destroyed fibres only. This evidence of callosal projection in visual cortex is possible exclusive at pd 20 with satisfying results. The neurons of laminae II and III project in the animals with a normal visus exactly to the contralateral 17/18a borderline. Enucleated mice show in area 18a two or three stripes more reaching laterally. Microphthalmic mice have terminals in both area 17 and 18a.