Comparative Study of the Sensory Areas of the Human Cortex (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 edition. Excerpt: ... collaterals during their ascent through the 5th layer, reach up to the extreme limit of the 5th layer and here become horizontal. There is no lack of fibres which ascend directly up to the limit of the layer of medium-sized pyramids and there describe arcs, and even very long wavy courses, and end by descending, dividing as they descend, through the 4th and 5th layers. Finally, from the arching portion of some of these latter fibres fine collat ends may be seen to spring on their way to the layer of medium-sized pyramids, where they disappear after a few divisions. To sum up, the optic fibres terminate almost exclusively within the 4th and 5th layers. In only two instances have I discovered collaterals of optic fibres which appeared to form their terminal arborizations within the 1st layer. This plexus of optic fibres is one of the richest and densest to be found in the gray matter of the brain. If it is completely impregnated, which frequently occurs in an infant brain fifteen or twenty days old, it appears as a bewildering meshwork of wavy fibres, besprinkled with vacant spaces corresponding to the cell bodies of these layers (Fig. 18, B). I may add that the, . Fin. 17.--Heavy fibres coming from the whit lahstanr 11118 and subdivldinK in Gennarl's stripe; visual cortex of infant aged plexus diffres a little three days. A, white substance; B, layer of small stellar calls;, I, . C, arched fibres of 4th layer; /). border of layer of medlam-J V ' sized pyramids; a, trunks of the incoming fibres; . collaterals 18). In the 4th layer for deeper layers; r, ascending collaterals destined fur the. more superticial layers. its fibres are larger and often disposed in arches or horizontal bars, ita arborizations are loose and separated by...