HYPOGLOSSAL GANGLIA OF PIG EMBRYOS 279 



later. I have frequently found it double, consisting of two spindle- 

 shaped masses of cells. Other spinal ganglia show the same con- 

 dition. The first cervical ganglion possesses always several 

 proximal roots (4-5) and the distal root arises as two distinct 

 bmidles. Froriep's ganglion never shows more than two proximal 

 roots, generally only one, and never more than one distal root. 

 As these ganglia are also spindle-shaped I would regard them as 

 not homologous with a spinal ganglion, but as comparable to one 

 of the spindle-shaped divisions of such a cervical ganglion as 

 seen in fig. 4. Two of the rudimentary hypoglossal ganglia with 

 their two distal roots would be exactly homologous with a single 

 spinal ganglion. The separation of the two parts of the ganglion 

 could be accounted for as due to their arrested development ; 

 as they do not appear until late and the pre-cervical region grows 

 more rapidly, the two masses of cells representing a ganglion 

 would be separated to a greater or less extent. At any rate, we 

 find that the first cervical ganglion is frequently divided in the 

 same way, sometimes the second cervical, and the same thing 

 may occur throughout the spinal series. The irregularities of 

 structure and constant variation which we find in the hypo- 

 glossal ganglia is merely typical of all rudimentary structures. 

 Lewis has objected that the connection of the hypoglossal 

 ganglia with the vagus is more marked than their relation to the 

 hypoglossal. He figures the hypoglossal ganglia (his " beaded 

 commissure") as continuous with the jugular ganglion. I have 

 shown that the direct connection with the jugular ganglion is 

 only important as showing their common development from the 

 neural crest. Occasionally this connection entirely disappears 

 and it is to be compared to the loops of cells which may persist 

 between the proximal roots of two adjacent spinal ganglia. Fur- 

 thermore as many as three ganglia may be connected by distal 

 roots with the roots of the hypoglossal. It is my opinion that the 

 anterior ganglia of this series originally related to the hypoglossal, 

 have become connected with the vagus complex, just as in man 

 some fibers from the first cervical ganglion have joined the spinal 

 accessorv. 



