FATIGUE IN NERVES. 157 



with Ringer's solution. As it was desired to stimulate the roots of each 

 side and as it is not convenient to use 2 pairs of electrodes in the limited 

 space, the plan was followed of stimulating one root and when it did not 

 give a response after 30 seconds rest it was immediately removed and 

 the second root laid on the same electrode. In all cases tried the 

 ganglionated root remained the better. Fig. 9 is a tracing taken 

 28 hours after the commencement of the experiment. The frog 

 responded throughout by a few (3 or 4) well sustained contractions 

 and then failed. On the first day (6 hours) the responses aggregated 

 the same, ll minutes from each. On the second day the responses up 

 to 12 o'clock, when the ligatured root failed, aggregated 2| minutes for 

 the ligatured and 7| minutes for the unligatured. After the tracing 

 was taken, which as the times above indicate was nearly two hours 

 after the previous stimulation, the unligatured root gave about two 

 minutes more contraction and a few slight ones the next day before the 

 frog died. 



The following table gives the results in those cases in which tracings 

 were taken. Many more experiments were made without tracings but 

 the time was only taken approximately. If the height and power of 

 the contractions were also considered the difference would be greater. 



It has been noticed 1 that the reflex applied to one place on the skin 

 soon becomes ineffective. In order to control my numbers a few 

 experiments were made by stimulating with induction shocks a given 

 spot of the skin in frogs whose forebrain had been removed. I usually 

 stimulated for 15 seconds and then waited till the frog quieted. The 

 responses are exactly like those from the dorsal root, in that one can 

 obtain a couple of minutes movement at a time and then no more until 

 a longer rest is allowed. The total response from such a spot during 

 6 hours was 6, 7, 9, and 11 minutes in the four cases tried. These 

 numbers correspond closely with those obtained during 6 hours from a 

 cut or uncut root. 



4. Effect of stimulating cut and uncut motor nerves. 



As it was suggested that the motor nerves should act in a similar 

 manner to the dorsal roots, some experiments were made with them in 

 the frog. The 3 strands of the pelvic plexus were cut on one side, or 

 the sciatic cut high in the thigh on one side and the electrodes placed 

 under the two sciatics low down in the thigh. The nerves were stimulated 

 1 See Sherrington, Text Book of Physiol., edited by Schiifer, n. p. 831. 



