4/0 "Joiiriwl of Comparative Neurology aiid Psycholocry . 



intention later to analyse in detail all these classifications and at 

 the present moment it is merely necessary to call attention to the 

 fact that in the spinal ganglion several varieties of cells have been 

 distinguished from one another. Can all these cells of different 

 varieties be considered as belonging to a single class or are there 

 really several types of cells composing the spinal ganglion ? In 

 other w^ords, a frequency of distribution of all these cells based on 

 their sizes' should give us more than one mode if there were more 

 than one type of cell involved. If but one mode appears we have 

 good ground to conclude that all these cells, though differing 

 in size as well as in structure, may be considered from the stand- 

 point of size, as members of a homogeneous population. The 

 differences in structure are for the moment neglected and must 

 form the subject of a special study. 



MATERIAL AND TECHNIQUE. 



For the present investigation the second cervical spinal ganglion 

 of the adult albino rat was employed. The second cervical gan- 

 glion was purposely selected since through the investigation of 

 R ANSON ('06) we have already some numerical data in regard 

 to this particular nerve. 



The second nerve with ganglion was removed from right side of 

 a healthy male having a body-weight of 194 grams and was fixed 

 with osmic acid. Following the usual procedure the sections of 

 the ganglion were cut 12 micra thick and mounted in series. 

 Fhree sections from the middle of the entire series of 80 sections 

 and three sections from midway between the middle and end on 

 both sides, thus making altogether nine sections, were chosen. 

 These nine sections were selected for the measurement of the cells 

 and nuclei on the assumption that the cells of the different sizes were 

 uniformly distributed and consequently that the nine sections 

 would adequately represent the total cell "population" of the 

 ganglion. 



The measurements obtained from each cell and its nucleus 

 were recorded on a separate card. In every case two maximum 

 diameters at right angles to each other were determined for both 

 cell-body and nucleus by means of the ocular micrometer. The 



' Although this point could be tested also from the standpoint of the structure, nevertheless it is very 

 difficult to obtain numerical liata in terms of the structure, suitable for biometric treatment. 



