HYPOGLOSSAL GANGLIA OF PIG EMBRYOS 273 



it passes under its proximal roots. Froriep's ganglion possesses 

 now one, now two proximal roots, with a distal bundle of fibers 

 entering the posterior root of the hypoglossal nerve, and it is 

 united to a more irregular ganglionic mass by a strand of cells 

 which varies in size in different embryos. This second ganglion 

 also shows one or two proximal roots, and a distal root is in evi- 

 dence. A third cell mass more cephalad shows a proximal root, 

 is pointed at its distal end and projects ventrad to the spinal ac- 

 cessory. Anterior to these three occurs a series of five cell masses, 

 more diffuse, more closely united and elongate in the anteropos- 

 terior line. A small strand of cells unites the more cephalad of 

 these to the jugular ganglion, and this in turn is connected with 

 the superior ganglion of the glossopharyngeal. Each of these 

 cell masses possesses from two to four proximal roots, and two 

 pairs of the adjacent roots are joined by cellular loops. Distal 

 roots either join the spinal accessory or form part of flattened 

 bundles which pass to the trunk of the vagus. 



In three of these five embryos the first cervical ganglion was 

 distinctly double as in figs. 4 and 5. In the other two it gave evi- 

 dence of a double origin. An interesting point was the difference 

 in structure exhibited on the right and left sides of the same em- 

 bryo. For example, in two other cases Froriep's ganglion was 

 well developed with a distal hypoglossal root on the right side, 

 small and without hypoglossal root on the left side. In two cases 

 no hypoglossal root was found on either side, a condition similar 

 to that figured by Lewis, who, however, found a small distal fiber 

 bundle in a second embryo. 



To sum up: The 13 mm. embryo shows (1) the neural crest 

 anterior to the first cervical ganglion differentiated into about 

 eight ganglionic masses; (2) the two posterior of these send roots 

 to the hypoglossal in the majority of cases, and the condition fig- 

 ured by Lewis is apparently the exception, rather than the rule; 

 (3) a persistence of cellular cords still unites the various links in 

 this chain of ganglia with each other and with the first cervical 

 and jugular ganglia; (4) the first cervical ganglion is often double 

 in structure, and all the spinal ganglia are elongate and unlike 

 the rounded nodules figured by Lewis; (5) in the ganglionic chain 



