112 Development of Occipital Nerves in Human Embryos 



system. The behavior of tlic nt'rvons system adds to tlie irregularity in 

 the line of junction between the head and trunk. 



As the accessorius wedges itself into the spinal territory there occurs 

 a progressive retrogression of the more oral spinal elements, resulting 

 in the disappearance of the dorsal roots and ganglia of the occipito-spinal 

 nerves, these being the first nerves encountered. The ventral roots of 

 these nerves persist and join to form the hypoglossus, and supply the 



Notochord 



Occipital rnyof-orries 



V^C m yofome. 



Cranial nervous 

 3 y stern in spinal 

 territory. 



Ih rr\yoforr\e-. 



Nervous System. 



Muscular 



Skeleia.1 



Fig. 14. Diagrammatic reconstruction of one month human embryo, lU.O mm. Ioiik-, Mall 

 collection No. 144. Enlarged 9 diams. 



tongue, which in the meantime has been acquired in the floor of the 

 mouth. In some of the domestic animals (rabbit, pig, cow, and sheep) 

 one or two of the more caudal of the occipito-spinal dorsal roots and 

 ganglia persist as was pointed out by Froriep, 82, whose name they have 

 received. In man the most caudal ganglion occasionally persists, but it 

 is usually without any connection with a corresponding ventral root; in 

 one case, however, a Froriep ganglion with ventral root was present, and 

 doubtless would have joined with the hypoglossus as its most caudal root. 



