Thank you for that interesting post. I think nowadays it's very important to stay flexible in our thinking. The biggest mistake would be an attitude like "We already know so much, what else can there be?" Medical knowledge has always been "in the flow". It also depends on how you define things, for example what is the definition of an organ? See Wikipedia: https://en.m.wikipedia.org/wiki/Organ_(anatomy)#Modern_definitions_and_ontology
RE: The Interstitium, the Largest Organ We Never Knew We Had The human body was thought to have 79 organs—until researchers stumbled on a strange phenomenon that could turn medicine and what we thought we knew about the body upside down.