216 ALBERT KUNTZ 



Kohn ('05, '07) describes the anlagen of the sympathetic trunks 

 in the rabbit as a pair of columns of cell-aggregates arising along 

 the sides of the dorsal surface of the aorta. Similar cells are found 

 in intermediate positions between these cell-aggregates and the 

 spinal nerves, in the paths later occupied by the fibers of the com- 

 municating rami. According to Kohn, the sympathetic anlagen 

 are composed of cells which arise by the division of elements which 

 have not migrated thither, but were differentiated in situ in 

 the spinal nerves. Embryonal neurocytes deviate from the 

 course of the spinal nerves toward the aorta. By division 

 they yield a syncytial cellular communicating ramus which 

 extends toward the aorta. Cell-groups become separated from 

 its distal end and give rise to the cell-aggregates of the sympa- 

 thetic anlagen. 



According to Neumayer's observations on embryos of Lacerta 

 (spec?) and the chick ('06), the anlagen of the sympathetic trunks 

 arise as short cellular outgrowths on the spinal nerves which early 

 develop ganglionic enlargements at their distal ends, which become 

 united later by longitudinal cellular commissures. Neumayer, 

 like Kohn, traces the origin of the sympathetic system directly 

 to the spinal nerves. He is of the opinion that in all vertebrates 

 the sympathetic anlagen arise from cells which are to be regarded 

 as the offspring of the dorsal and the ventral nerve-roots and are 

 differentiated in situ, like the cells of the spinal ganglia and the 

 fibers of the nerve-roots. 



The work of Froriep ('07) on embryos of Torpedo and of the 

 rabbit, marks a decided advance in our knowledge of the histo- 

 genesis of the sympathetic nervous system. He succeeded in 

 tracing medullary cells peripherally along the ventral roots of 

 the spinal nerves. These cells he formerly interpreted as elements 

 which give rise to the neurilemma. After Harrison C04) showed 

 experimentally that in amphibians the cells giving rise to the neu- 

 rilemma of both the sensory and the motor fibers have their origin 

 in the neural crest, Froriep concluded that the cells migrating 

 peripherally in the ventral nerve-roots, either alone or with cells 

 which wander out from the spinal ganglia, give rise to the sym- 

 pathetic nervous system. In his summary he expresses the opin- 



