A stereotaxic atlas h a s been prcpared of the forebrain of the guinea pig (body weight 700-830 9 ) using a standard cat-monkey stereotaxic instrument. The coordinates used were t h e vertical interaural planc (APO) and the horizontal orbital-interaural planc ( H O ) . The atlas consists of transverse sections of the brain taken a t 0.5 m m intervals from A5 through A15.
Although stereotaxic atlases have been published for many species of laboratory animals, a search of the literature failed to reveal a n atlas of the guinea pig brain. In this department it has recently become desirable to use the guinea pig for studies on the neuroendocrine control of lactation. This species is well suited to the purpose, since unlike the rabbit or rat, it has only two mammary glands, each with a discrete vascular and nervous supply. To facilitate our studics a stereotaxic atlas has been prepared of the forebrain of the guinea pig. J , S . TINDAL Figs. 2-23 Tracings from projections of transverse sections of guinea pig forebrain at 0.5 mm intervals from 5 mm to 15 mm anterior to the antero-posterior zero (APO) plane. Height and lateral scales are i n mm.
AB, basal amygdala N. AC, anterior commissure ACE, central amygdala N. ACO, cortical amygdala N. AD; anterodorsal thalamic N. AHA, anterior hypothalamic area AL, lateral amygdala N. AM, anteromedial thalamic N. AME, medial amygdala N. AQ, aqueduct ARC, arcuale hypothalamic N. AV, snteroventral thalamic N. BSC, brachium of superior colliculus C, central thalamic N . CA, caudate N. CC. corpus callosurn CG, central grey CL, claustrum CORT, iieocortex CSC, commissure of superior colliculus D. Darkschewitsch N. DBB, diagonal band of Broca T , manimillo-tegmental tract TOL, lateral olfactory tract TPT, transverse peduncular tract TS; tecto-spinal tract VDM, ventro-dorso-medial thalamic N. VL: ventro-lateral thalamic N. VM, ventro-medial thalamic N . VMH, ventromedial hypothalamic N. VTD, ventral tegmental decussation 21, zona incerta