Dr Lanyon is a genial man and was once a great friend to Dr Jekyll. Lanyon is passionately attached to his scientific certainties and disagrees with Jekyll's theories which Lanyon describes as "scientific balderdash".
In contrast Jekyll considers him "hidebound" (conventional and unadventurous) in his attitude towards medical science. This causes the men to fall out and not talk for over ten years.
When Lanyon witnesses Hyde's transformation back into Jekyll he cannot cope with the fight between his sensible, rational view of the world and what he sees before him. This is more than his mind can bear and he falls ill ultimately never to recover.
|"I wish to see no more of Dr Jekyll… I am quite done with that person; and beg you will spare me any allusion to one whom I regard as dead."||After watching his transformation, Lanyon is shocked to his core and wants no more to do with him.|
|"This was a hearty, healthy, dapper red-faced gentleman".||This early description of Lanyon contrasts with the later one after he has witnessed the transformation.|
|"Henry Jekyll became too fanciful for me. He began to go wrong, wrong in mind..."||Lanyon details why he fell out with Jekyll and how he disapproved of the research he was doing.|
|"unscientific balderdash".||Lanyon is meticulous in his own scientific studies and dismisses what Jekyll is doing.|
|"the rosy man had grown pale; his flesh had fallen away"||This description of Lanyon after he has seen the transformation is in stark contrast to the description of him as hearty and healthy.|
|"I have had a shock and I shall never recover..."||Lanyon cannot comprehend what he has witnessed when he sees the transformation.|