CRANIAL SYMPATHETIC GANGLIA IN THE PIG 



75 



is well differentiated. The nuclei of the cells composing the 

 ganglionic mass are identical in appearance with the nuclei of 

 the majority of the cells in the mantle layer in the neural tube. 

 In general the nuclei in the ganglion are oriented so that their 

 long axes are directed peripherally. This orientation, however, 

 is by no means constant. 



■,■■"'* *,"^'--' 







Fig. 2 Parasagittal section showing semilunar ganglion and the main divi- 

 sions of the trigeminal nerve in an embryo of the pig 8 mm. in length. Max, 

 maxillary nerve; Man, mandibular nerve; 0, oral cavity; Op/t, ophthalmic nerve; 

 SeTTi, Semilunar ganglion. 



In parasagittal sections of embryos of the pig 8 mm. in length, 

 the three main divisions of the trigeminal nerve may be traced 

 peripherally for a considerable distance (fig. 2) . The ophthalmic 

 division is composed of a slender bundle of fibers which may be 

 traced anteriorly above the upper margin of the optic vesicle 

 into the region of the orbit (fig. 2, OyK). The maxillary division 

 is composed of loosely aggregated bundles of fibers which may 

 be traced anteriorly above the oral cavity as far as the anterior 

 margin of the optic cup (fig. 2, Max). This division emerges 



