160 F. H. SCOTT. 



activity in the cells of the spinal cord, also examined these cells from 

 Steinach's experiments and he also could observe no changes. The 

 failure of Steinach and Pick to observe changes in these cells is due, 

 I believe, to the fact that Steinach had cut the dorsal roots before 

 stimulating the nerve, and there were, therefore, no changes produced. 



I have made a number (12) of experiments on this point and I 

 believe both of these observations are correct. In most cases I cut and 

 excited the central end of one of the nerves in the pelvic plexus, having 

 first in some cases cut the dorsal root close to the cord. The stimula- 

 tion was applied usually for 30 seconds and then 30 seconds rest. This 

 was repeated as long as reflexes were obtained if the root were exciting 

 or about 10 times if the root were cut. Three or four of these groups 

 of stimulations were given during 4 or 5 hours. The two corresponding 

 ganglia were then put through the same fixing fluids, imbedded together 

 and cut and stained at the same time. In other cases I cut the root on 

 one side and the corresponding nerve in the plexus on that side. On 

 the opposite side two nerves were cut. One corresponding to the cut 

 nerve on the opposite side (this to prevent the muscular movements 

 exciting the cells) and the other nerve for stimulation. The two nerves 

 one on each side were stimulated equally by means of a commutator 

 and then the corresponding ganglia fixed and compared as in the first 

 case. Changes similar to those described by Hodge and Holmgren 

 could be found when the dorsal root had been exciting the cells in the 

 cord, but no changes were observed when the root had been cut before 

 the stimulation. Similar observations were also made in the rabbit, 

 but as all my material has not yet been examined a more complete 

 discussion of this point is reserved for a future occasion. 



6. Some points regarding the double (crossed and simple) reflexes. 



In most cases the direct reflex was obtained with considerably 

 weaker current than that required for the crossed reflex. In some 

 cases this difference was very slight and in two or three cases the 

 crossed reflex seemed easier to obtain. If in a fresh frog a root is 

 stimulated with a current strong enough to obtain reflexes in both 

 legs, the crossed side is observed to come to rest before the direct side 

 (Fig. 10). 



The reverse of the above may occur in a frog in which one has fatigued 

 the direct side without having caused the crossed reflex. If the current 

 be then increased, the crossed reflex is obtained while the direct reflex 



