SYMPATHETIC NERVOUS SYSTEM IN MAN 195 



Sphenopalatine ganglion 



The primordium of the sphenopalatine ganghon arises at the 

 growing tip of the greater superficial petrosal nerve as an aggre- 

 gate of cells which advance from the geniculate ganglion along 

 the path of this nerve. The earliest human embryos in which it 

 was observed are 11 mm. in length (nos. 619 and 1836). The 

 geniculate ganglion is not sharply limited dm'ing early develop- 

 ment, but cells advance from its distal border along the fibers of 

 the great superficial petrosal nerve. Cells of this type are present 

 throughout the entire length of this nerve; consequently, it pre- 

 sents, during these early stages, the appearance characteristic 

 of a slender nerve trunk along which cells of cerebrospinal origin 

 advance peripherally. 



This primordium of the sphenopalatine ganglion lies medial 

 to, but not in contact with the maxillary nerve. This nerve is 

 composed of numerous loosely aggregated bundles of fibers. Cells 

 become separated from the semilunar ganglion and advance per- 

 ipherally along these fiber bundles either singly or in small aggre- 

 gates. In embryos 12 to 15 mm. in length rami deviate from the 

 maxillary nerve near its origin from the semilunar ganglion and 

 grow into the primordium of the sphenopalatine ganghon. Cells 

 of ganglionic origin advance along these rami and become aggre- 

 gated at their growing tips. This condition, as it appears in 

 coronal sections of an embryo 14.6 mm. in length (no. 1919), is 

 illustrated in figure 23. Sections which cut the maxillary nerve 

 approximately at right angles at the level of the sphenopalatine 

 ganglion in embryos 15 mm. and over in length show a fibrous 

 ramus accompanied by numerous cells of nervous origin which 

 extends from the maxillary nerve into the primordium of this 

 ganglion. The same condition still obtains in embryos 20 and 21 

 mm. in length (nos. 462 and 460). Figures 8, 24, 25, and 26 are 

 taken from sections of these embryos which show both a maxil- 

 lary ramus and the nerve of the pterygoid canal, which comprises 

 the fibers of the greater superficial petrosal nerve, growing into 

 the primordium of the sphenopalatine ganglion. They show 

 clearly that numerous migrant cells are still present along the 



