[A morphological study of the mammalian parasolitary nucleus]

A comparative anatomical study of the parasolitary nucleus (Kohnstamm & Wolfstein, 1907) using Weigert-Pal-Carmine or Nissle sections of mammalian brain-stem was made to discover its precise topography and cytoarchitecture. In transverse planes, the nucleus is usually found on the ventral side of the solitary tract. The parasolitary cells can be found not only among the solitary cells, but in the solitary tract, and in the parvocellular reticular formation (Fig. 1 a-f & 4). The oval or drop shaped parasolitary cells can be easily identified because they are nearly as large as the hypoglossal cells (Table 1). The cells of the solitary nucleus and parvocellular reticular formation are only one half to two thirds as large as the parasolitary cells. In sagittal planes, the mammalian parasolitary nucleus is one to four fifths as long as the hypoglossal nucleus. Its most developed part can be found somewhat oral to the obex (Fig. 1 h & 5). A Golgi study of the cat parasolitary nucleus was also made, using Golgi-Rapid and Golgi-Cox serial sections. Three-dimensional reconstruction with serial sections was attempted as far as possible. The dendrites of the cat parasolitary cells are thick and straight with blunted tips. They show only a few ramifications. The longest dendrite extends as far as 700 micrometers. The directions of the dendrites are variable. Each cell has eight to ten dendrites. Few spines can be observed (Fig. 2 a, b). The dendritic field of the parasolitary nucleus, as a whole, extends dorsally into the middle layer of th solitary nucleus, ventrally into the parvocellular reticular formation, medially into the intercalate nucleus, and laterally into the inferior nucleus of the vestibular nerve.