The ultrastructure of the 'peripheral resistance' and the precapillary sphincters

The vascularization of the primary somaesthetic cortex of the albino rat was studied by snap-fixing of the vessels with a constant infusion of glutaraldehyde through the left ventricle of the heart, followed by injection of a resin under a constant pressure and flow rate directly into the aorta. The vibrissae on one side were stimulated both before and during the fixing procedure. Specimens of the appropriate area of the cortex were taken and treated for viewing by scanning electron microscopy. The apparent morphological changes are described and illustrated by micrographs.