I cannot be sure, but I believe that is the reason why Edward Hyde was so much smaller than Henry Jekyll. But that was not the only difference between the two men. Henry Jekyll had a kind, open, honest face. Pure evil stared out of Edward Hyde's eyes. I felt no dislike, however. Indeed, I welcomed him. Edward Hyde was me, young and strong and full of life.
Later, however, I noticed that Hyde's appearance and manner had a strong effect on other people. Nobody could meet Edward Hyde without a feeling of dislike and horror. I believe I understand the reason for this too. Everyone is a mixture of good and evil. Even the worst criminal has a little good in him. Only Edward Hyde was pure evil.