Morphology and development of the postdiaphragmatic part of the sympathetic trunk in the pig (Sus scrofa L.) during its prenatal period.

The experiment was conducted on 36 swine fetuses divided into the three developmental groups described by Marrable (1971). In the postdiaphragmatic part, 10 to 20 primary ganglia were found in the sympathetic trunk. They had fused with the secondary structures, and hence the sympathetic trunks studied finally consisted of 6-16 ganglia. It is remarkable that the higher number of primary ganglia did not correspond with the higher number of secondary ones. The variation in the number of secondary ganglia was mainly connected with the interganglionic fusion occurring in the section studied. The standard variation in the length of the sympathetic ganglia increased considerably with the age of the fetuses as well as the analogous coefficient of variation. The analysis of the statistical parameters referring to the ganglia of the investigated section of the sympathetic trunk investigated indicated the growth of its developmental dynamics, which did not occur until the terminal period of gestation.