Quantitative histological studies on the lateral geniculate nucleus in the cat. IV. Numerical aspects of the transfer from restinal fibers to cortical relay.

The numerical data, gained both from the quantitative histology and Golgi stained material was completed with those of optic fibers. The number of X and Y fibers was estimated on the basis of our results, on the data of literature and from the ratio of the large and medium size relay neurons. The crossed and uncrossed fibers were counted and compared with the number of relay neurons in layer A and A1. Knowing the different numerical and metrical counts of neuronal elements in LGN of cat some calculations were carried out on the overlaping of optic fiber arborizations, on the intersections of dendritic ramification points of relay neurons and on the spatial arrangement of both the optic terminals and the relay neurons. The comparison of the neumerical data on relay neurons and optic fibers and their relations were the basic factors of considerations on divergence and convergence of retinal input.