GANGIJON CELLS IN THE SYMPATHETIC SYSTEM 271 



less than seven; but none of these authors has clearly differen- 

 tiated a distinct sensory type of cell, although Michailow re- 

 gards as sensory some of the dendritic endings found by him. 

 In general, the various forms observed have been looked upon 

 as variations of the motor elements, due largely to differences in 

 the character of the dendrites and in the lobation or fenestration 

 of the cell-bodies. 



The present work was undertaken to confirm, if possible, by 

 means of the silver-nitrate and Nissl methods, the existence of 

 Dogiel's sensory and motor types in the sympathetic system of 

 mammals. Dogiel's description of these elements as seen after 

 methylene blue staining will be given in connection with the ac- 

 count of our own observations. 



SYMPATHETIC GANCxLION CELLS OF THE CAT (CAJAL SILVER- 

 NITRATE METHOD) 



As Dogiel's observations were made on methylene blue mate- 

 rial it was thought advisable to check them first with a silver 

 impregnation method. For this purpose the silver-nitrate re- 

 duction process of Cajal was employed. One advantage of this 

 method for the complete study of the elements of a ganglion lies 

 in its tendency to differentiate, in successful preparations, all the 

 cells — not merely a few here and there as is so often the<fcase with 

 methylene blue staining. A disadvantage, however, must be rec- 

 ognized in the opacity of the tissue caused by the general deposi- 

 tion of the reduced silver. As a result thinner sections must be 

 cut than when methylene blue is used, in order that the individ- 

 ual cells may be clearly seen under the microscope. With such 

 comparatively thin sections (10 to 20 micra) the processes of 

 cell-bodies often cannot be followed distally as far as is desirable. 



In spite of the limitations of the method, Dogiel's two types of 

 cells can clearly be made out in Cajal preparations of the superior 

 cervical ganglion of the cat. For instance, figure 1 is easily 

 recognizable as his motor type, described as possessing a round, 

 oval, fusiform or stellate cell-body, often more or less compressed, 

 from which are given off from 5 to 20 comparatively thick and 



