and a greater proportion of tlio nuclei stain red in the 

 cord of the stimulated frog. A count of all the red 

 and all the blue nuclei in a large number of sections 

 shows that 3.31 to 3. 06 times more nuclei stain red in the 

 stimulated than in the unstimulated frog. The results 

 are derived from four frogs, two stimulated and two 

 control. 



We gather from this brief resume that nerve tissue 

 of the frog, crawfish, dog and man has been examined 

 with special reference' to the observation of changes 

 occurring in it. The main points noted up to date are, 

 first, changes in the appearance of the living nucleus ; 

 second, vacuolation and shrinkage of the cell proto- 

 plasm and also of the axis cylinder; and third, that 

 the nuclei in the spinal cord of a stimulated and 

 unstimulated frog stain somewhat differently. 



Method of Investigation. 

 The value of results, especially in this branch of 

 histology, depends so much upon the soundness of the 

 method employed, that a somewhat detailed descrip- 

 tion of some features of my method must be given. I 

 have used in all cases the spinal root ganglia. My 

 scheme of procedure has been throughout to stimulate 

 electrically a nerve going to one or more of these 

 ganglia on one side of the animal, leaving the corres- 

 ponding parts on the other side at rest. To avoid 

 possible confusion, the right side was invariably used 

 for stimulation, the left for control. At first a double 

 control was used, consisting of the corresponding gang- 

 lia from a similar animal of the same size and sex. 

 This practice was soon abandoned, however, for it 

 was found that the ganglion cells of two frogs that 

 could not be distinguished externally might differ 



