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 t hat analyze medullary neuronal groups, and factors that influence variabili ty in the location of neuronal groups were determined. The medullas of 31 a dult goats (weight, 17-88 kg) were fixed, harvested, frozen, serially secti oned, 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 medi olateral coordinates of medullary neuronal groups were determined, whereas dorsoventral coordinates mere calculated from the medullary surface. Histol ogical variations with goat body weight were quantified, and linear regress ion analysis provided adjustment factors for weight in all three dimensions . Similar analysis of percentage of shrinkage on fixation and processing pr ovided adjustment factors for precise coordinates of medullary neuronal. gr oups. For accurate location of neuronal groups, body weight and histologica l procedure should be taken into account. The present study provided adjust ment factors for body weight and standard histological processing to locate most major medullary neuronal groups in the adult goat.