CRANIAL SYMPATHETIC GANGLIA IN THE RAT 177 



did not become apparent until later, when the glossopharyngeal 

 nerve was studied. In examining cells in and along the vagus 

 trunk, one finds numerous shapes and sizes which are apparently 

 intermediate between the elongate type of cell and the cell in 

 which cytoplasmic development and general nuclear shape pre- 

 sent clearly the characteristics of a neuroblast. These cells 

 possess nuclei showing bendings, constrictions, and tendencies 

 toward the assumption of a spherical shape, apparently corre- 

 lated with cytoplasmic increase. Vagus fibers are very rich in 

 these elongate elements and their apparent modifications, and 

 it is seemingly through transformation of this indifferent type 

 of cell that the majority of neuroblasts along the vagus trunk 

 arise. In recognizing these elongate cells as elements closely 

 resembling the 'indifferent cells of Schaper' the writer agrees 

 with the interpretation of Kuntz. Only occasionally does one 

 encounter a neuroblast, other than large elements — seemingly 

 aberrant sensory cells — in the upper portion of the vagus trunk; 

 elongate cells and their earlier types of modification are found, 

 however, throughout. The more definitive neuroblastic cells 

 occur lower down, particularly at and below the origin of the 

 inferior laryngeal nerve, in the lower esophageal and upper 

 gastric regions. Here the differentiation process apparently is 

 at a maximum, and in later stages — fifteen-day embryos — large 

 accumulations of neuroblasts may be found along the vagus 

 trunk in the lower esophageal region (fig. 23). This ganglionic 

 mass figured is alone larger than any definitive ganglion of the 

 sympathetic chain at this stage. A similar ganglionic mass has 

 been described by Abel ('09) in a five-day chick embryo. Miss 

 Abel likewise noted similar cells higher up in the vagus trunk, 

 but failed to interpret them of vagus origin; she derived the 

 ganglia of the alimentary canal entirely from the trunk sympa- 

 thetic ganglia. 



Embryos of fifteen and three-quarter days, especially those 

 in the preparation of which special techniques have been em- 

 ployed, have been most useful. It is quite advantageous to 

 compare pyridine-silver preparations, which give excellent fiber 

 pictures, with the results of some excellent cytoplasmic fixer, 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO. 3 



