An anatomic atlas of the medulla oblongata of the adult goat.

An anatomic atlas of the goat brain stem was developed for use in studies that analyze medullary neuronal groups, and factors that influence variability in the location of neuronal groups were determined. The medullas of 31 adult goats (weight, 17-88 kg) were fixed, harvested, frozen, serially sectioned, stained with 0.5% neutral red, and examined with a light microscope. Obex, the point at which the central canal opens into the fourth ventricle, was taken as the zero reference point from which the rostrocaudal and mediolateral coordinates of medullary neuronal groups were determined, whereas dorsoventral coordinates were calculated from the medullary surface. Histological variations with goat body weight were quantified, and linear regression analysis provided adjustment factors for weight in all three dimensions. Similar analysis of percentage of shrinkage on fixation and processing provided adjustment factors for precise coordinates of medullary neuronal groups. For accurate location of neuronal groups, body weight and histological procedure should be taken into account. The present study provided adjustment factors for body weight and standard histological processing to locate most major medullary neuronal groups in the adult goat.