The author made experiments to find out wheter the dilation of blood-vessels of a frog's webs is really due to the antidromic action or not when mustard oil is applied to the N. ischiadicus of the amphibian. The results are as follows: 1. Cut the N. ischiadicus at the central part before it unites with the R. communicans, making the nerve fall into degeneration, and then apply mustard oil to it, and you will see that the blood-vessels contracts. 2. Cut R. communicans, making it fall into degeneration, and then apply mustard oil to the nerve, and you will see that the blood-vessels dilates. From the above stated facts, it is plain that the dilation of the blood-vessels of a frog's webs is due to the antidromic action.