Several cell masses around the commissura anterior in the chicken

In the course of cytoarchitectonic studies on the hypothalamus of the fowl, 6 cell masses which may be respectively considered as one nucleus, were newly found around the commissura anterior (CA). They were provisionally designated nuclei A-F in this study. In the frontal sections, nucleus A was a grape-like cell mass composed of the smallest round cells in the lateral preoptic area. Nuclei B and D were the most deeply stained cell masses showing round shapes. The former was located immediately rostral to the CA and consisted of cells oriented dorsoventralward, while the latter, situated dorsal to the CA, were composed of cells oriented rostrocaudalward. In contrast to the other 5 deeply stained and compact cell masses, nucleus C was the most poorly stained cell group. It was composed of two types of cells which were located around the margin of the CA. Under the CA, nucleus E was found to be the broadest cell mass composed of densely located cells. Further caudally, nucleus F was also found as a compact cell mass consisting of the poorly stained and densely located cells.