166 FRED W. STEWART 



the obvious logical difficulty in arguing from the incompletely 

 demonstrated 'law of neurobiotaxis' to the likewise physio- 

 logically undemonstrated 'law of prevalence of the axon-reflex.' 

 The second group of interpretations, i.e., where it is sought 

 to recognize in certain cerebrospinal ganglia, or in the central 

 nervous system, representatives of sympathetic ganglion cells, has 

 become quite prevalent. Perhaps the most emphatic advocate 

 of this belief is C. K. Hoffmann ('00). Hoffmann's conclusions 

 may be briefly summarized in the following statements : 



1. The formation of the sympathetic ganglion in the trunk 

 region is contingent upon the union of posterior and anterior 

 nerve roots to form a mixed trunk. 



2. In the majority of head segments this union does not occur. 



3. The ramus ophthalmicus V, constituting a purely dorsal 

 sensory nerve, unites with a purely ventral motor nerve, the 

 oculomotor and, as a result of the union, the ciliary ganglion 

 is formed. 



4. Since, however, motor and sensory portions of the tri- 

 geminus, facialis, glossopharyngeus, and vagus nerves unite 

 within the central organ, they issue therefrom as mixed nerves, 

 and may, therefore, at their origin give rise to sympathetic 

 ganglia. The great peripheral ganglia of these nerves are con- 

 sequently mixed cerebrospinal and sympathetic, these including 

 jugular, nodose, petrosal, geniculate, sphenopalatine, otic, and 

 submaxillary. The ciliary ganglion alone is purely sympathetic. 



The interesting fact in Hoffmann's interpretation is that the 

 single ganglion he has concluded to be entirely sympathetic in 

 nature, the ciliary, is the only one about which serious doubt 

 regarding its single value has definitely existed. 1 



1 Krause ('81) advocated the double nature of the ciliary ganglion. Retzius 

 '81 I described bipolar cells in the ciliary ganglion of the chick, but believed that 

 of the cat purely sympathetic; in 1894 Retzius confirmed his observations. Holtz- 

 iiiaiin ('96) found bipolar cells in the ciliary ganglion of the frog, the chick, and 

 the dog ; he considered t he ganglion mixed cerebrospinal and sympathetic. Car- 

 penter ('06) believed that the ciliary ganglion of the chick consisted of two por- 

 t ion-, one of bipolar cells and t he second of cells typically synipal het ic in charac- 

 ter. Carpenter's later work (II i failed to confirm the observation. Galvao 

 ('17) described the ciliary ganglion of ophidians as consisting of strictly unipolar 

 cells. 



