Important note that won't matter as soon as the next page is published: Lanyon did not just teleport out of the room. The answer to "what happened to Lanyon between panels 4 and 5?" will be answered next week.
The conversation that Jekyll and Jasper start at the bottom of this page took the longest to solidify of any section of this chapter. I had planned for a very long time for Jekyll to explain his working philosophy on life to Jasper using the cabinets as a metaphor. Whenever I tried to write it down, it kept ballooning out into this rambly speech--the contents of which I honestly can't remember very well--but I never felt like it got to the point of whatever I meant to say. In the end, this conversation ended up much shorter than I originally thought it would be and--next week spoiler alert--ends up focusing on something more character based than concept based. Which I think is better.
The concept behind what Jekyll is saying--that you can be as monstrous as you like on the inside so long as you look respectable on the outside--is really just a more practical version of what Jekyll told Jasper in Chapter 2, but hopefully it goes a little way to explain one of the meanings behind The Glass Scientists (the title, not the story).