Abstract: The present study is an attempt to further ascertain the histological locationand afferent connections of the"Groaning Center"of the cat. In 1952,by electrical stimulation of the lateral tegmental area of cats,arestricted region was found to give rise to the groaning response and itwas designated as the"Groaning Center",which on excitation would alsoproduce various viseral and motor reactions. According to our microscopic study of the position of the"GroaningCenter",we found that the pars lateralis of the nucleus subcuneiformis inthe lateral tegmental region is the focal point of the center.It lies ventrala-teral to the nucleus trochlear,medial to the lateral lemniscus and the nucleusparalemniscalis (Jasper atlas,1954),dorsal to the nucleus cuneiformis.Thiscenter extends about 1.0mm.anteroposteriorly,1.0mm.mediolaterally andabout 1.5mm.dorsoventrally.This area cheifly consists of fibers and scatteredcells of medium and small size.A cluster of larger cells has been observed inthe ventral region of the center. By HRP retrograde transport study,we found that after injection ofHRP into the center,the reactive cells were found in extensive brain areas.The labelled cells were mainly found in the ipsilateral side of the hypothala-mus,especially in the lateral and posterior nucleus of hypothalamus as wellas the dorsomedial nucleus of hypothalamus.The reactive cells were also foundin the forebrain regions,such as the cingulate gyrus,globus pallidus,zonaincerta,nucleus parafascicularis,etc. The relation between the center with vocalization and emotionalresponses is discussed.

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