Hardestv, spinal Ganglion Cells. 19 



('98) mentions a distal excess of 25% in the IXth spinal nerve 

 of the frog. 



An investigation of the numerical relations of the axones 

 on the two sides of the spinal ganglion naturally suggests an 

 inquiry as to the number of ganglion cells in it and the relation 

 they bear to the numerical arrangements of the fibers. This pa- 

 per is offered with the hope of contributing something (i) to the 

 knowledge of the relations between the number of the nerve 

 fibers in the dorsal roots and the number of ganglion cells in 

 the spinal ganglia whence the fibers are supposed to arise ; (2) 

 toward throwing further light upon the conditions determining 

 the excess of fibers on the distal side of the spinal ganglion ; 

 and (3) concerning the influence of growth upon the relative 

 number of ganglion cells and the numerical relations of the 

 fibers in the region of the ganglion. 



The investigation was begun some time ago when the au- 

 thor was connected with the neurological laboratory of the Uni- 

 versity of Chicago. It has been allowed to rest on account of 

 the difficulty in obtaining the material required. Rana vircsccns 

 having been employed in the beginning of this and and the previ- 

 ous papers with which the results of this must be compared, it was 

 thought advisable to continue with this species though it is ap- 

 parently very rare in California. It finally became necessary 

 that the material from the specimens of the sizes required to 

 complete the work be sent from the laboratory in Chicago, and 

 I desire to thank Professor Donaldson and Dr. Dunn for their 

 kindness and care in obtaining it for me. 



Finally, let it be said that the author realizes that the re- 

 sults of an investigation of this kind are valueless unless ob- 

 tained by most trustworthy procedure. 



II. Material and technique. 



Ouly three of the spinal nerves of each frog are dealt with. These 

 are the Vth, Vlth, and IXth of each of seven frogs varying in weight 

 from 10.4 to 63.4 grams. The Vth was chosen as a typical thoracic 

 nerve and because, being near the lumbar region, its dorsal and ven- 

 tral roots are long enough to render manipulation less difficult. The Vlth 

 nerve in many respects is similar to the thoracic nerves anterior to it. 



