To begin with I would like to express our thanks to Lord Adrian for his most kind invitation for our group of Fellows of the Academy of Sciences of the U.S.S.R. to visit Great Britain. I am also obliged to him for his having proposed me to deliver to-day’s lecture. I must confess that I have experienced some difficulty in the choice of the subject-matter, as I could not decide which of the different branches of my experimental studies would be preferred to be reported on. I understood too well that any particular subject chosen would be of interest only to a few specialists concerned. And I again thank Lord Adrian who has helped me to choose the subject of this report from two topics proposed by me as corresponding to certain research work carried out in Great Britain.