I believe you made an error on page 30. Both the man handing the medicine over and the patient (the child) are demons. it makes no sense for him to say " i don't know how effective this demon medicine will be since human and demon biology is different" as again, the only non demon involved is not the patient. it should be something more along the lines of 'human biology is different from demons ' as an explanation as to why she should use this medicine instead of human medicine or her healing magic.
Or if I'm comparing to the other scalation, he's talking about how each demon is very different from one another and that inspires less confidence in whether his medicine will work on this child. in this case I believe you should enthesis that he is talking about the difference in physiology between demon individuals rather than how it is now where it seems he's just again saying that humans and demons are dissimilar.
EDIT: I suppose another interpretation could be that since he sells products to humans, he would have only human medicine on hand? but that seems unlikely. over all I think the text should be changed to make the meaning more clear.